Hi everyone I am working on a game and I have run into a really weird issue and was hoping to get some help. Basically sometimes the text is a bit long to show in one textbox so I wanted it to break down a string and store the undisplayed text in a string to be used in the next message box. So when I use this code..
NSString * Talkin1 = #"Hello I am an annoying string";
NSString * Talkin2 = [Talkin1 substringToIndex:5];
It makes Talkin2 the value of Hello which is what I want. Then I store it in the object with..
[_window setMultiMessage:Talkin2];
which goes to my set and get methods in an object i made.
In it's interface...
NSString * multiMessage;
in its .m
-(void) setMultiMessage:(NSString*)messageTwo
{
multiMessage = messageTwo;
}
-(NSString*) getMultiMessage
{
return multiMessage;
}
then later the main object pulls it out again, when it is done closing the first window with...
NSString * talking = [_window getMultiMessage];
Now in debugging, I have noticed talking's value will be "out of scope" when i get the string back from _window. So then it crashes my program when it tries to use it.
But. If i do this everything works fine.
NSString * Talkin1 = #"Hello I am an annoying string";
//NSString * Talkin2 = [Talkin1 substringToIndex:5];
[_window setMultiMessage:Talkin1];
So it works perfect (except for splitting the string like I want) when I use #" " but not when I use any result of substringToIndex or substringFromIndex.
I am new to objective c so I assume it is something basic I am missing. Any help would be wonderful! Thank you in advance.
(Assuming no GC.)
-substringToIndex: returns an autoreleased object. But you are not retaining the object in the setter, thus no one "owns" the Talkin2 and it will be deallocated "later". You need to copy or retain the string in the setter.
-(void) setMultiMessage:(NSString*)messageTwo {
if (multiMessage != messageTwo) {
[multiMessage release];
multiMessage = [messageTwo retain];
}
}
Actually you should really use Objective-C 2.0's declared property feature. It allows correct setter and getter be generated automatically.
#interface .... { ... }
...
#property(copy) NSString* multiMessage; // <--
...
#end
#implementation ....
#synthesize multiMessage; // <--
...
#end
...
_window.multiMessage = Talkin2;
// or: [_window setMultiMessage:Talkin2];
NSString* talking = _window.multiMessage;
// or: talking = [_window multiMessage];
Related
I'm trying to follow team treehouse's course on objective-C.
This part, the course is trying to teach us about implementing categories. So I have the code below
main.m
#import <Cocoa/Cocoa.h>
#import "NSArray+mahem.h"
int main()
{
NSArray *letters = #[ #"alfa", #"bravo", #"charlie"];
NSLog(#"letters %#", letters);
NSLog(#"cap %#", [letters capitalizeStrings]);
return 0;
}
NSArray+mahem.h
#import <Foundation/Foundation.h>
#interface NSArray (mahem)
-(NSArray *)capitalizeStrings;
#end
NSArray+mahem.m
#import "NSArray+mahem.h"
#implementation NSArray (mahem)
-(NSArray *)capitalizeStrings{
NSMutableArray *cap = [NSMutableArray array];
for (NSString *string in self) {
[cap addObject:[string capitalizedString]];
}
return cap;
}
#end
Basically, I am trying to capitalize every word in the NSArray letters. However, when I run main.m in xcode 6, the program reaches a breakpoint at the line for (NSString *string in self) { in the file NSArray+mahem.m.
I have never used the xcode debugger before, so am unsure what I'm seeing or how I should fix this. It seems to say that self does have 3 objects (#"alfa", #"bravo", #"charlie"), but cap has 0, and string apparently equals 0xa1a1a1a1. I'm assuming this means it broke on the first loop, or else cap would have at least one object. Why did string get gibberish?
Is this because NSArray is const and is not mutable? How do I fix this? If anyone can explain this to me, it would be very helpful. Thanks
From your description, everything works just fine. When execution flow gets to the string for (NSString *string in self) {
Your self array is fully populated - it was created previously in main()
Your cap has been declared and initialized, but not populated - for loop wasn't executed once.
Your string was declared but not initialized - it exists, but points to some random place in memory. It is not broken. If you'll step over in debugger, you will see, that string becomes #"alpha", but cap is still empty. One more step over - string is still #"alpha" and cap is populated with one object.
Everything should work fine. Feel free to ask anything left unclear
I wrote a BinaryReader class in Objective-C that can extract an NSString from bytes created using C#'s BinaryWriter.Write(string). It seems to work great, but when I call:
BinaryReader *binaryReader = [[BinaryReader alloc] initWithData:dataArray];
NSString *strName = [binaryReader readString];
// strName is not nil, but the value is no longer correct (seems to have been erased)
I stepped into the readString method, and everything looks great (the string is correct) up until the method returns (I think ARC is kicking in).
Why would this be happening?
Here's my readString method:
-(NSString *)readString
{
NSUInteger bytesCount = (NSUInteger)[self read7BitEncodedInt];
const void *byteData = [_data bytes] + _dataIndex;
NSString *returnValue =
[[NSString alloc] initWithBytes:byteData length:bytesCount encoding:NSUTF8StringEncoding];
_dataIndex += bytesCount;
return returnValue;
}
The returnValue contains the proper string right before the method returns.
By request, here's my init function for BinaryReader.
-(id)initWithData:(NSData *)theData
{
self=[super init];
if(self != nil)
{
_dataIndex = 0;
_data = theData;
}
return self;
}
and the relevant part of header
#interface BinaryReader : NSObject
{
#private
NSData *_data;
int _dataIndex;
}
Are you sure the result is actually broken? The code you posted seems fine and there should be no ownership/memory issues when compiled with ARC.
Lately there have been issues reported with lldb (the debugger) not showing correct values in some cases. Try to log the result using NSLog.
ARC should not release the object so soon, so your error might be inside the readString itself.
Put your binaryReader as a property with the strong attribute, it may solve your problem.
#propert(nonatomic, strong) BinaryReader* binaryReader;
It tell to the compil to not release the object.
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.
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.)
So I have all this code that I have debugged and it seems to be fine. I made a mutable string and for some reason I can not get it to be displayed on my label. the debugger says
"2010-04-22 22:50:26.126 Fibonacci[24836:10b] *** -[NSTextField setString:]: unrecognized selector sent to instance 0x130150"
What is wrong with this? When I just send the string to NSLog, it comes out fine.
here's all my code, any help would be appreciated. "elementNum" is a comboBox and "display" is a Label.
Thanks
#import "Controller.h"
#implementation Controller
- (IBAction)computeNumber:(id)sender {
int x = 1;
int y = 1;
NSMutableString *numbers = [[NSMutableString alloc] init];
[numbers setString:#"1, 1,"];
int num = [[elementNum objectValueOfSelectedItem]intValue];
int count = 1;
while (count<=num) {
int z = y;
y+=x;
x=z;
[numbers appendString:[NSString stringWithFormat:#" %d,", y]];
count++;
}
[display setString:numbers];
NSLog(numbers);
}
#end
`
Look at the error message you're getting:
-[NSTextField setString:]: unrecognized selector sent to instance 0x130150"
This is telling you something. Specifically, that NSTextField does not have a -setString: method and trying to call it will fail.
This is your cue to look at the docs for NSTextField. When you do so, you will see that there are no methods to set the string value. However, the docs also show you that NSTextField inherits from NSControl, which has a -setStringValue: method.
So, you need to call -setStringValue: to set the value of an NSTextField.
[display setStringValue:numbers];
Note that in your code at present, you are leaking the numbers string object. You created it using -alloc, so you are responsible for releasing it.
Instead, you should create it using [NSMutableString stringWithString:#"1, 1,"], which will return an autoreleased object, as well as initializing it in the same message.