I'm new to Objective C and iOS development in general, so if I missed some information that needs to be included please let me know and I'll do my best. At the same time, if any of my assumptions are incorrect or if I set this up totally dumb, please don't hesitate to yell at me. Thanks!
I have a class object called feeds. Here's how I initialize it in the .h file:
#interface ClassViewController : ContentViewController <UITableViewDelegate,
UITableViewDataSource> {
NSMutableArray *feeds;
}
#property (nonatomic, strong) NSMutableArray* feeds;
and in the .m:
#dynamic feeds;
I'm trying to get results from JSON and load them up into the feeds. Let's assume that resArr has correct data in it:
NSArray *resArr = [results objectForKey:#"data"];
if([self->feeds count]) {
[self->feeds removeAllObjects];
[self->feeds addObjectsFromArray:resArr];
}
else {
self->feeds = [[NSMutableArray alloc] initWithArray:resArr];
}
Now, this works fine the first time (i.e., the first time I put data into the array), but I get the following error subsequent times: *** -[NSMutableArray addObjectsFromArray:]: array argument is not an NSArray
I'm clueless. Any ideas?
Edit: JSON structures
1:
{"code":200,"data":[{"name":"ABM"},{"name":"ACC"}]}
2:
{"code":200,"data":{"100":{"subject":"ABM","title":"Decision Making in Agri-Food"},"130":{"subject":"ABM","title":"Farm Management I"}}}
you should use self.feeds instead of self->feeds, here's a good read Dot (“.”) operator and arrow (“->”) operator use in C vs. Objective-C
are you sure the subsequent times are actually NSArrays?
edit additon
Looks like the first JSon is just a array of names, where's as the second is a dictionary keyed with 100, 200, etc. So the JSON converts this into a dictionary keyed to 100, 200, ...
NSArray* resArr = [results objectForKey:#"data"];
if([self.feeds count]) {
[self.feeds removeAllObjects];
if([resArr isKindOfClass:[NSDictionary class]])
[self.feeds addObjectsFromArray:resArr.allValues];
else
[self.feeds addObjectsFromArray:resArr];
}
else {
self.feeds = [[NSMutableArray alloc] initWithArray:resArr];
}
Related
Assume, your .h file looks like this:
#property (retain, nonatomic) NSMutableArray *songs;
- (NSMutableArray *)popularSongs;
- (void)make20PercentDiscountToPopularSongs
Your .m file looks like this:
- (NSMutableArray *)popularSongs
{
NSMutableArray *popularSongs = [NSMutableArray array];
for (Song *song in self.songs) {
if (song.isPopular) {
[popularSongs addObject:song];
}
}
return popularSongs;
}
- (void)make20PercentDiscountToPopularSongs
{
for (Song *song in self.popularSongs) {
song.price = song.price * 0.8;
}
}
The code above adds a 20% discount to popular songs. I recognise that there is a more simplistic way of doing this. You could have the "make20PercentDiscountToPopularSongs" and "popularSongs" function in a single function but let's assume that the code is written the way it is written above.
In the example above, will the line:
song.price = song.price * 0.8;
Actually, make any changes to the object:
#property (retain, nonatomic) NSMutableArray *songs;
Or not? Because, it seems as if the line will change the newly created popularSongs NSMutableArray rather than the songs NSMutableArray, am I right? This problem is bothering me for a lot of time now. I would like to make changes just to the original songs array. To me popularSongs works as if you are storing the pointers to the songs in the songs array.
It changes neither array. It changes some of the objects in the songs array. And as the same objects are in the popularSongs array returned then they are 'changed' too.
This:
[popularSongs addObject:song];
Adds the pointer to the current song into the array. It doesn't create a new copy of the song.
You can create a quick mutable array like this:
NSMutableArray *popularSongs = self.songs.mutableCopy;
Rather than iterating through all the songs to determine if they are popular, you could use a filter predicate at the time you create the array.
NSMutableArray *popularSongs = [[self.songs filteredArrayUsingPredicate:
[NSPredicate predicateWithFormat:#"isPopular = %#", #YES]] mutableCopy];
With this one-liner you can avoid your methods altogether ;-)- Not sure what you want, but if you want to alter the original songs, leave out the mutableCopy part.
I am trying to remove a pointer in an NSMutableArray that points to an object in another array without deleting the object itself. E.g.:
// In ViewController.m – Code abridged and somewhat simplified
#interface ViewController ()
#property (nonatomic, strong) NSMutableArray *objectPool;
#property (nonatomic, strong) NSMutableArray *objectsOwnedByFriend;
#property (nonatomic, strong) NSMutableArray *objectsOwnedByMe;
- (void)transferPointerToObjectFromFriendToMe;
- (void)copyPointerToObjectFromFriendToMe;
#end
#implementation ViewController
#synthesize objectPool = _objectPool;
#synthesize objectsOwnedByFriend = _objectsOwnedByFriend;
#synthesize objectsOwnedByMe = _objectsOwnedByMe;
- (void)setObjectPool:(NSMutableArray *)objectPool
{
_objectPool = objectPool;
}
- (NSMutableArray *)objectPool
{
if (!_objectPool) _objectPool = [[NSMutableArray alloc] initWithArray:self.objects]; // self.objects is a mutable array containing multiple NSObjects
return _objectPool;
}
- (void)setObjectsOwnedByFriend:(NSMutableArray *)objectsOwnedByFriend
{
_objectsOwnedByFriend = objectsOwnedByFriend;
}
- (NSMutableArray *)objectsOwnedByFriend
{
if (!_objectsOwnedByFriend)
{
_objectsOwnedByFriend = [[NSMutableArray alloc] init];
[_objectsOwnedByFriend addObjectsFromArray:self.objectPool];
}
return _objectsOwnedByFriend;
}
- (void)setObjectsOwnedByMe:(NSMutableArray *)objectsOwnedByMe
{
_objectsOwnedByMe = objectsOwnedByMe;
}
- (NSMutableArray *)objectsOwnedByMe
{
if (!_objectsOwnedByMe) _objectsOwnedByMe = [[NSMutableArray alloc] init];
return _objectsOwnedByMe;
}
- (void)transferPointerToObjectFromFriendToMe
{
[self.objectsOwnedByMe addObject:[self.objectsOwnedByFriend lastObject]];
[self.objectsOwnedByFriend removeLastObject];
}
- (void)copyPointerToObjectFromFriendToMe
{
[self.objectsOwnedByMe addObject:[self.objectsOwnedByFriend lastObject]];
}
#end
In the above code, when I use transferPointerToObjectFromFriendToMe, removing the last object removes both the pointer to it in self.objectsOwnedByFriend (as I want) and also the object itself in self.objectPool (which I don't want to happen).
What I would like is an array (self.objectPool) that contains all of the actual objects and then two mutable arrays (self.objectsOwnedByFriend and self.objectsOwnedByMe) that contains pointers to objects in self.objectPool and the ability to add and remove more pointers referencing objects in self.objectPool to self.objectsOwnedByFriend and self.objectsOwnedByMe.
Also, when I use either transferPointerToObjectFromFriendToMe or copyPointerToObjectFromFriendToMe, the object doesn't seem to be added properly, as a subsequent check via self.objectsOwnedByMe.count results in 0 instead of 1.SOLUTION = My lazy instantiation for self.objectsOwnedByMe was missing in my original code :SI was able to check whether self.objectsOwnedByMe was properly created via:
NSLog(#"self.objectsOwnedByMe = %#", self.objectsOwnedByMe);
** My first StackOverflow question! ** I hope I was clear...couldn't find a a similar question so apologies if I missed an old thread. Let me know if you need more info to diagnose. (I am trying to learn Obj-C.)
Typo :P Sorry peeps. In my actual code in Xcode I had:
- (void)setObjectPool:(NSMutableArray *)objectPool
{
_objectPool = objectPool;
}
- (NSMutableArray *)objectPool
{
if (!_objectPool) _objectPool = [[NSMutableArray alloc] initWithArray:self.objects];
return _objectsOwnedByFriend;
}
I think my mistake is super obvious (and if not, the mistake was that my getter for objectPool was returning _objectsOwnedByFriend...copy/paste error that I somehow missed).
Everything works now!
This is very peculiar and confusing code. I suspect the problem is that something is calling one of the setters, -setObjectPool: or -setObjectsOwnedByFriend:, with the array of the other object. Those setters simply make the ivar refer to the object that was passed in. Because of that, they are very prone to lead to objects being shared.
Typically, a property like that would be declared and implemented with copy semantics.
It looks like self.objectsOwnedByMe is never initialized and you are therefore always working with nil instead of an actual NSMutableArray.
Somewhere (perhaps in a custom getter for objectsOwnedByMe as below?) you need to create an array before you start using it:
- (NSMutableArray *)objectsOwnedByMe {
if (_objectsOwnedByMe == nil) {
_objectsOwnedByMe = [[NSMutableArray alloc] init];
}
return _objectsOwnedByMe;
}
This would explain both problems: Since it is nil it never retains the objects and therefore they go away when removed from the other array, and also why they are never added to the _objectsOwnedByMe array.
Here is my code:
I want to be able to create a global NSMutableArray that can store Budget* objects that can then be written to a .pList file... I'm only learning what pLists are, and I am a bit hazy about how to implement them...
Where am I going wrong here?
- (IBAction)btnCreateBudget:(id)sender
{
Budget *budget = [[Budget alloc] init];
budget.name = self.txtFldBudgetName.text;
budget.amount = [self.txtFldBudgetAmount.text intValue];
// Write the data to the pList
NSMutableArray *anArray = [[NSMutableArray alloc] init]; // I want this to be a global variable for the entire app. Where do I put this?
[anArray addObject:budget];
[anArray writeToFile:[self dataFilePath] atomically:YES];
/* As you can see, below is where I test the code. Unfortunately,
every time I run this, I get only 1 element in the array. I'm assuming
that this is because everytime the button is pressed, I create a brand new
NSMutableArray *anArray. I want that to be global for the entire app. */
int i = 0;
for (Budget * b in anArray)
{
i++;
}
NSLog(#"There are %d items in anArray",i);
}
-(NSString *) dataFilePath
{
NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDirectory = [path objectAtIndex:0];
return [documentDirectory stringByAppendingPathComponent:#"BudgetData.plist"];
}
edit: I'd like to add that I am creating the anArray array so that it can be accessible by other views. I understand that this can be done with NSNotification? or Should I do this the appDelegate classes? The end goal is to have the anArray object populate a UITableView that is in a separate View.
Just put the declaration outside the method instead of inside it.
NSMutableArray *anArray = nil;
- (IBAction)btnCreateBudget:(id)sender
{
...
if ( anArray == nil )
anArray = [[NSMutableArray alloc] init];
...
}
If it's only used inside the one file, make it "static" instead to prevent name collisions with other files:
static NSMutableArray *anArray = nil;
If it's only used inside the one method, make it "static" and put it inside that method:
- (IBAction)btnCreateBudget:(id)sender
{
static NSMutableArray *anArray = nil;
...
if ( anArray == nil )
anArray = [[NSMutableArray alloc] init];
...
}
Note that people usually use some kind of naming convention for global variables, like "gArray", to easily differentiate them from local variables, instance variables, or method parameters.
Global variable is not necessary in this case. You can do something like this:
Read old data to mutable array (initWithContentsOfFile:).
Add new record to the array.
Save the array to same file.
But the second problem in your code is that if your Budget class is not a property list type (NSString, NSData, NSArray, or NSDictionary objects) writeToFile: will not save it sucessfully.
You need to make sure that your Budget class invokes NSCoder and then the NSCoder initWithCoder: and NSCoder decodeWithCoder: methods. Otherwise, writeToFile: will not work for you NSObject class.
But I digress. The answer to the original question should be the following.
In your .h file you need to do the following.
#interface WhateverClassName : UIViewController
{
NSMutableArray *anArray;
}
#property(nonatomic, retain) NSMutableArray *anArray;
#end
Then, you need to make sure you #synthesize the NSMutableArray so that you don't get any freaky warnings. This is done just after the #implementation line in your .m file.
Then, within the function that you want it to be allocated into memory, simply do the following.
anArray = [[NSMutableArray alloc] initWithObjects:nil];
This is now a global variable. It is global in the sense that it can be used from any function and is not limited to use in one function.
If you would like to have data accessible to the entire application or context ("global"), you can use a singleton. However, do this with care and make sure it is actually necessary and appropriate. I would suggest doing plenty of reading up on it prior to any implementation of a singleton. Carter Allen has a good basic implementation here.
According to "The end goal is to have the anArray object populate a UITableView that is in a separate View" you wouldn't need to write anything to a file, database or singleton. Just set the object. Like stated by Sebastien Peek.
If you wish for offline data storage, look into sqlite, json, plist , etc
I'd like to add search functionality to a TableView in my app. I populate a table with an NSArray which has x amount of Objects that contain 3 NSStrings. Here's how I construct that NSArray:
First I create a class Code.h:
#import <Foundation/Foundation.h>
#interface Code : NSObject
#property (nonatomic, strong) NSString *codeName;
#property (nonatomic, strong) NSString *codeNumber;
#property (nonatomic, strong) NSString *codeDesc;
#end
Next, I synthesize these NSStrings in Code.m.
Now in my SearchViewController.m, Here's how I create my dataset:
NSMutableArray *codes;
codes = [[NSMutableArray alloc] init];
Code *c = [[Code alloc] init];
[c setCodeNumber:#"1"];
[c setCodeName:#"First Title Here"];
[c setCodeDesc:#"I might write a desc in here."];
[codes addObject:c];
c = [[Code alloc] init];
[c setCodeNumber:#"2"];
[c setCodeName:#"Second Title Here"];
[c setCodeDesc:#"2nd desc would be written here."];
[codes addObject:c];
and so on...
Here is how I display it: cellForRowAtIndexPath:
Code *c = [codes objectAtIndex:indexPath.row];
NSString *fused = [NSString stringWithFormat:#"%# - %#",[c codeNumber],[c codeName]];
cell.textLabel.text = fused;
return cell;
So now that you know how my data is structured and displayed, do you have an idea of how to search either the NSArray or possibly (preferably) the TableCells that have already been created?
I have been through the few tutorials online regarding Adding a Search Bar to a TableView, but all of them are written for using arrays setup using simple arrayWithObjects.
SIDETHOUGHT: Is it possible for me to construct an arrayWithObjects:#"aaa-1",#"bbb-2",#"ccc-3"... from my data? If i can manage that, I can use those tutorials to populate my cells and search them!
UPDATE:
Your second answer makes plenty more sense to me! Thanks for that. I beleive I have followed your instruction, but I am getting a "-[Code search:]: unrecognized selector sent to instance 0x6a2eb20` when that line is hit.
I added #property (nonatomic, strong) NSString *searchString; to Code.h and synthesized it in Code.m
I added NSMutableSet *searchResults; to SearchViewController.h's #interface
I added your methods performSearchWithString and matchFound to SearchViewController.m
Directly under those I added this to call performSearchWithString
x
- (void)searchBar:(UISearchBar *)theSearchBar textDidChange:(NSString *)searchString {
NSLog(#"%#",searchString); //Just making sure searchString is set
[self performSearchWithString:searchString];
[self.tableView reloadData];
}
The error hits when [codes makeObjectsPerformSelector:#selector(search:) withObject:self]; runs. I am confused b/c it sounds like Code doesn't recognize searchString, but I know I added it in Code.h.
UPDATE:
In order to store objects in searchResults, I had to change searchResults from a NSMutableSet to a NSMutableArray and modify - (void)matchFound:(Code *) matchingCode {} to this:
-(void) matchFound:(Code *) matchingCode {
Code *match = [[Code alloc] init];
if (searchResults.count == 0) {
searchResults = [[NSMutableArray alloc] init];
[match setCodeName:[matchingCode codeName]];
[match setCodeNumber:[matchingCode codeNumber]];
[match setCodeDesc:[matchingCode codeDesc]];
[searchResults addObject:match];
}
else
{
match = [[Code alloc] init];
[match setCodeName:[matchingCode codeName]];
[match setCodeNumber:[matchingCode codeNumber]];
[match setCodeDesc:[matchingCode codeDesc]];
[searchResults addObject:match];
}
With a few other tweeks, I've got a working searchbar for my tableView. Thanks Tim Kemp!
Oh, also case insensitive search was what I was looking for. NSRange rangeName = [codeName rangeOfString: searchString options:NSCaseInsensitiveSearch];
I hope this question and answer will be helpful to the next developer learning objective-c with this question!
Simpler approach
You asked for a simpler solution. This one isn't nearly as flexible, but it will achieve the same things as my earlier answer for this specific case.
Once again we are going to ask Code to search its strings for us. This time, we are going to skip the SearchRequest and the block callback and implement it directly.
In your SearchViewController you will create two methods. One to do the search, and one callback to process any results as they come back. You will also need a container to store matching Code objects (more than one might match, presumably.) You will also need to add a method to Code to tell it what the search string is.
Add an ivar NSMutableSet called searchResults to SearchViewController.
Add a property of type NSString * called searchString to Code
Add the search method to SearchViewController. This is what you'll call when you want to initiate a search across all your codes:
-(void) performSearchWithString:(NSString *) searchString {
// Tell each Code what string to search for
[codes makeObjectsPerformSelector:#selector(setSearchString:) withObject:searchString];
// Make each code perform the search
[codes makeObjectsPerformSelector:#selector(search:) withObject:self];
}
Then you will also need a callback in SearchViewController. This is so that your Code objects can tell the SearchViewController that they have found a match:
-(void) matchFound:(Code *) matchingCode {
[searchResults addObject:matchingCode];
// do something with the matching code. Add it to a different table
// view, or filter it or whatever you need it to do.
}
However do note that you don't have to use the searchResults mutable set; you may well want to just call another method to immediately add the returned result to some other list on screen. It depends on your app's needs.
In Code, add a search method a bit like we had before, but instead of the SearchRequest parameter we'll pass in a reference to the SearchViewController:
- (void) search:(SearchViewController *) searchVC {
// Search each string in turn
NSRange rangeNum = [codeNumber rangeOfString : searchString];
NSRange rangeName = [codeName rangeOfString : searchString];
NSRange rangeDesc = [codeDesc rangeOfString: searchString];
if (rangeNum.location != NSNotFound || rangeName.location != NSNotFound || rangeDesc.location != NSNotFound) {
[searchVC matchFound:self];
}
}
Do you see how that works? If there's a match in any of the strings (|| means 'or') then pass self (which means exactly what it sounds like: the current object that's running this code right now) back to a method in the view controller called searchVC. This is called a callback because we are "calling back" to the object which originally sent us the message to do the search. We have to use callbacks rather than simple return types because we have used makeObjectsPerformSelector to tell every single Code in the codes array to do a search. We never explicitly called the search method ourselves, so we have no way to capture the return value from each search. That's why its return type is void.
You can extend matchFound to take an additional parameter which identifies which string the match was in (i.e. çodeNumber, codeName or codeDesc.) Look into enums as one good approach to pass around that kind of data.
Hope that's bit simpler.
Here is a link to an excellent language introduction/tutorial which will eliminate much confusion.
EDIT In your last comment you said that searchResults was null. I said to add it as an ivar somewhere in SearchViewController. In your initialiser method for SearchViewController you should call
searchResults = [[NSMutableSet alloc] initWithCapacity:50]` // Choose some sensible number other than 50; enough to hold the likely number of matching Code objects.
Alternatively you could 'lazy initialise' it in matchFound:
- (void) matchFound:(Code *) matchingCode {
if (!searchResults)
searchResults = [[NSMutableSet alloc] initWithCapacity:50];
[searchResults addObject:matchingCode];
}
Though if you do this you should be aware that anywhere else you access searchResults may find that it's null if matchCode: has never previously been called.
Original, flexible and more complicated answer
I'm a little unclear as to what you're trying to do, so I'm going with your title, "Searching each string in each object of an array." In your case, your Codes have three strings and your array has multiple Codes. I assume that you need a way to tell the caller - the code that wants to do the search - which Code matches.
Here is one approach. There are easier ways but this technique is quite flexible. Broadly, we are going to make the Code object do the work of searching its own strings. We are then going to give the Code object the ability to tell the caller (i.e. the object that owns the codes array, presumably your table view controller) whether any of its strings match the search string. We will then use NSArray's method makeObjectsPerformSelector to have to tell all of its Code objects to search themselves. We will use a block for a callback.
Firstly, add a search method to Code (in the interface, or as a category depending on your design), something like this:
-(void) search:(SearchRequest *) request {
// Search using your favourite algorithm
// eg bool matches = [searchMe [request searchString]];
if (matches) {
[request foundMatch:self];
}
}
SearchRequest is new. It's a place to tie together a search string and a callback block. It looks something like this:
#interface SearchRequest
#property (retain) NSString * searchString;
#property (copy) void (^callback)(Code *);
- (id) initWithSearchString:(NSString *) search callback:(void (^)(Code *)) callback;
- (void) foundMatch:(Code *) matchingCode;
#end
#implementation SearchRequest
// synthesize...
// initialiser sets ivars
- (void) foundMatch:(Code *) matchingCode {
callback(matchingCode);
}
The callback block is our way of communicating back to the caller.
When you want to perform a search, construct a SeachRequest object with the string you're searching for and a block which contains the method to call when you get a match.
That would look like this, in the caller:
- (void) performASearchWithString:(NSString *) searchForMe {
SearchRequest * req = [[SearchRequest alloc] initWithSearchString:searchForMe
callback:^(Code * matchingCode) {
[self foundAHit:matchingCode];
}];
[codes makeObjectsPerformSelector:#selector(search:) withObject:req];
}
You then need to implement foundAHit in your caller, which takes the matching Code and does something with it. (You don't have to use a block: you could store a reference to the caller and a selector to call on it instead. I won't go into the arguments for either case here. Other answerers can propose alternatives.)
I am curious how I might override the description method that is used when you do the following (see below) for an object. I basically want to better format the output, but am unsure about how I might go about setting this up.
NSLog(#"ARRAY: %#", myArray);
many thanks
EDIT_001
Although subclassing NSArray would have worked I instead decided that I would add a category to NSArray (having not used one before) Here is what I added ...
// ------------------------------------------------------------------- **
// CATAGORY: NSArray
// ------------------------------------------------------------------- **
#interface NSArray (displayNSArray)
-(NSString*)display;
#end
#implementation NSArray (displayNSArray)
-(NSString*)display {
id eachIndex;
NSMutableString *outString = [[[NSMutableString alloc] init] autorelease];
[outString appendString:#"("];
for(eachIndex in self) {
[outString appendString:[eachIndex description]];
[outString appendString:#" "];
}
[outString insertString:#")" atIndex:[outString length]-1];
return(outString);
}
#end
gary
If you're doing this a lot, the easiest way to reformat the display of your array would be to add a new prettyPrint category to the NSArray class.
#interface NSArray ( PrettyPrintNSArray )
- (NSSTring *)prettyPrint;
#end
#implementation NSArray ( PrettyPrintNSArray )
- (NSString *)prettyPrint {
NSMutableString *outputString = [[NSMutableString alloc] init];
for( id item in self ) {
[outputString appendString:[item description]];
}
return outputString;
}
#end
Obviously you'd need to alter the for loop to get the formatting the way you want it.
I'm assuming that you myArray variable is an instance of the NSArray/NSMutableArray class.
When NSLog() encounters the # character in its format string, it calls the -description: method on the object. This is a method on the root class, NSObject from which all other Cocoa classes inherit. -description: returns an NSString allowing any object that implements this method to be passed into NSLog(#"#",anyObject) and have a nicely formatted output. The string returned can be anything you care to construct.
For your specific problem, you could subclass NSMutableArray and override the -description: method with your own implementation. Then utilise your subclass instead of NSMutableArray.
For more information on NSObject and -description: see Apple's docs.
From Formatting string objects:
NSString supports the format characters defined for the ANSI C functionprintf(), plus ‘#’ for any object. If the object responds to the descriptionWithLocale: message, NSString sends that message to retrieve the text representation, otherwise, it sends a description message.
So to customize array conversion to string you should change NSArray descriptionWithLocale: implementation. Here's an example of how you can replace object method in run-time.