i am using the addToolTipRect: method to set a tooltip rect
- (NSToolTipTag)addToolTipRect:(NSRect)aRect owner:(id)anObject userData:(void *)userData
and method stringForToolTip: to obtain string value for tooltip.
- (NSString *)view:(NSView *)view stringForToolTip:(NSToolTipTag)tag point:(NSPoint)point userData:(void *)data
However the above functions work fine if i send something like
[self addToolTipRect:someRect owner:self userData:#"Tool tip string"];
But doesn't work when i send the following string. Error: BAD_ACCESS
const NSString * tooltipStr = #"Tool tip string";
[self addToolTipRect:someRect owner:self userData:tooltipStr];
In both the cases, the stringForToolTip looks like:
- (NSString *)view:(NSView *)view stringForToolTip:(NSToolTipTag)tag point:(NSPoint)point userData:(void *)data
{
id obj = (id)data;
NSString * str=nil;
if ([obj isKindOfClass:[SomeClass class]]) //This is my system defined class and works fine
{
SomeClass * someClassObj = (SomeClass *) data;
str = someClassObj.title;
}
else if([obj isKindOfClass:[NSString class]])
str = (NSString*)obj;
return str;
}
NOTE: In the stringForToolTip: method I also want to check for some other class example [obj isKindOF:[SomeClass class]] and i don't want to assert that value. The problem here is just in getting the string value by proper cast but I can't figure out how! Please tell me where I am going wrong?
edit:
What should be the right way to get the String value for tooltip in that case? should the point or tag be considered?
(void *) is not an object pointer.
That #"Tool tip string" worked was by coincidence based on the fact that is is a compile-time constant with a (essentially) permanent allocation and permanent address.
But in the code:
const NSString * tooltipStr = #"Tool tip string";
[self addToolTipRect:someRect owner:self userData:tooltipStr];
tooltipStr is an object that is kept in memory by a strong reference (retain count > 0). Since userData: does not handle objects it does not make a strong reference (does not increase the retain count) so it is released, will disappear soon becoming invalid.
Notes from the documentation:
The tooltip string is obtained from the owner. The owner must respond to one of two messages, view:stringForToolTip:point:userData: or description, use the latter. Note that NSString responds to description so you can pass an NSString for the value of owner. So, what you want is: [self addToolTipRect:someRect owner:tooltipStr userData:NULL];. There is still an issue that something must hole a strong reference to the NSString instance.
You can: [self addToolTipRect:someRect owner:#"Tool tip string" userData:NULL];
Probably the best way to go is to pass self as owner and NULL as data and implement the delegate method: view:stringForToolTip:point:userData: in the class.
Related
I am passing an ivar (NSMutableArray) into some method. I was expecting that if I modify the object inside the function, it would be reflected outside the function, but in this case I need to set the object; something like the following:
- (void) someMethod:(SMResponseObject *)response onData:(NSMutableArray *)imAnIvar {
imAnIvar = [response objects];
//Some other stuff
}
But I noticed that the memory reference of imAnIvar inside the function changes when I set it, and given that, the actual ivar doesn't change. I understand that the problem is that I'm changing the reference of the object inside the method, so it stops pointing to the ivar and then it points to some other random memory direction.
I thought about one solution to this problem, and it can be to ensure that the ivar is not nil before calling the function and do something like this:
- (void) someMethod:(SMResponseObject *)response onData:(NSMutableArray *)imAnIvar {
NSMutableArray *data = [response objects];
[arrayForTableView removeAllObjects];
for(id element in data){
[imAnIvar addObject:element];
}
//Some other stuff
}
So I use the original object instead of setting it directly. The problem is that in order for this to work I need to ensure that the ivar is not nil, which I think is not clean, because I'll need to do something like this on every call to the method:
if(!_ivar){
//alloc it
}
So my question is: Is there a way to force the local scope variable to point to the original variable even if I'm setting it? if not, is there any cleaner way to make this work?
Do you mean this?
- (void)setFoo:(SomeClass **)objPtr
{
*objPtr = someOtherObject;
}
// call it as:
SomeClass *foo = someObject;
NSLog(#"Before: %#", foo);
[self setFoo:&foo];
NSLog(#"After: %#", foo);
Why not use a getter for the array so that you need not check for the array being nil while using it?
-(NSMutableArray *)iAmAnIvar {
if(_iAmAnIvar == nil) {
_iAmAnIvar = [NSMutableArray array];
}
return _iAmAnIvar;
}
And when you have to set a value to the array, as you mentioned in your question, you could use
[self.iAmAnIvar removeAllObjects];
[self.iAmAnIvar addObject:someObj];
I believe you can use the - (id)copy; function of NSObject
so your code might look like this:
- (void)someFunction:(NSString *)someArg
{
NSString *str = [someArg copy];
}
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 have this question here (as well other quesrtions on SO), and the Apple docs about Objective-C collections and fast enumeration. What is not made clear is if an NSArray populated with different types, and a loop is created like:
for ( NSString *string in myArray )
NSLog( #"%#\n", string );
What exactly happens here? Will the loop skip over anything that is not an NSString? For example, if (for the sake of argument) a UIView is in the array, what would happen when the loop encounters that item?
Why would you want to do that? I think that would cause buggy and unintended behavior. If your array is populated with different elements, use this instead:
for (id object in myArray) {
// Check what kind of class it is
if ([object isKindOfClass:[UIView class]]) {
// Do something
}
else {
// Handle accordingly
}
}
What you are doing in your example is effectively the same as,
for (id object in myArray) {
NSString *string = (NSString *)object;
NSLog(#"%#\n", string);
}
Just because you cast object as (NSString *) doesn't mean string will actually be pointing to an NSString object. Calling NSLog() in this way will call the - (NSString *)description method according to the NSObject protocol, which the class being referenced inside the array may or may not conform to. If it conforms, it will print that. Otherwise, it will crash.
You have to understand that a pointer in obj-c has no type information. Even if you write NSString*, it's only a compilation check. During runtime, everything is just an id.
Obj-c runtime never checks whether objects are of the given class. You can put NSNumbers into NSString pointers without problems. An error appears only when you try to call a method (send a message) which is not defined on the object.
How does fast enumeration work? It's exactly the same as:
for (NSUInteger i = 0; i < myArray.count; i++) {
NSString* string = [myArray objectAtIndex:i];
[...]
}
It's just faster because it operates on lower level.
I just tried a quick example... Here is my code.
NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:1];
NSNumber *number = [NSNumber numberWithInteger:6];
[array addObject:number];
[array addObject:#"Second"];
Now if I simply log the object, no problem. The NSNumber instance is being cast as an NSString, but both methods respond to -description, so its not a problem.
for (NSString *string in array)
{
NSLog(#"%#", string);
}
However, if I attempt to log -length on NSString...
for (NSString *string in array)
{
NSLog(#"%i", string.length);
}
... it throws an NSInvalidArgumentException because NSNumber doesn't respond to the -length selector. Long story short, Objective-C gives you a lot of rope. Don't hang yourself with it.
Interesting question. The most generic syntax for fast enumeration is
for ( NSObject *obj in myArray )
NSLog( #"%#\n", obj );
I believe that by doing
for ( NSString *string in myArray )
NSLog( #"%#\n", string );
instead, you are simply casting each object as an NSString. That is, I believe the above is equivalent to
for ( NSObject *obj in myArray ) {
NSString *string = obj;
NSLog( #"%#\n", string );
}
I could not find precise mention of this in Apple's documentation for Fast Enumeration, but you can check it on an example and see what happens.
Since all NSObject's respond to isKindOfClass, you could still keep the casting to a minimum:
for(NSString *string in myArray) {
if (![string isKindOfClass:[NSString class]])
continue;
// proceed, knowing you have a valid NSString *
// ...
}
How do I declare and use small helper functions inside my normal methods ?
In on of my objective-c methods I need a function to find an item within a string
-(void) Onlookjson:(id) sender{
NSString * res = [[sender gstring] copy];
persInfoBirth.text = getKeyValue(res, #"Birth");
}
I came up with a normal C type declaration for helper function getKeyvalue like this
NSString * getKeyvalue(NSString * s, NSString * key){
NSString *trm = [[s substringFromIndex:2] substringToIndex:[s length]-3];
NSArray *list = [trm componentsSeparatedByString:#";"];
//....
NSString res;
res = [list objectAtIndex:1];
//...
return res;
}
Example input string in s:
s=#"{ Birth = "1910"; Death = "1936"; }";
Anyway I get an exception "unrecognized selector sent to instance" for any of the two first lines in the helper function
How do I declare helper functions that are just to be used internally and how to call them safely ?
regards
Martin
Is this the real code? Do you get zero errors and warnings from the compiler? You must not ignore compiler warnings and you should turn on the Static Analyser in addition to the standard warnings.
There are many things wrong with the above code, most of which are nothing todo with declaring and calling methods. There is no way the above code could compile so maybe it pasted incorrectly or something..
Anyway.. declaring and using methods. Why are using a c function? Unless you have a good reason why not use Objective-c ? If you do have a good reason to use a C function the your definition should be:-
NSString *getKeyvalue( NSString *s, NSString *key ){
...
}
note the arguments. As NSString instances reside in the heap (not on the stack) you always want to pass pointers to them.
You then need to put the declaration in the header file:-
NSString *getKeyvalue( NSString *s, NSString *key )
EDIT:
In Objective-c there is no distinction between normal methods and helper methods, there is only one kind, and you have aleray written one
- (void)onLookJson:(id)sender { .. }
Taking it apart..
All methods begin with + or –, indicating Class method or Instance method. As you are familiar with C++ i guess you know what this means.
(void) is the return type. ie this method doesn't return a value. If it did it might look like (float) or (NSString *) or (id).
onLookJson: is the method name and the method takes 1 argument. Notice that the ':' is actually part of the name. This method is never is any circumstance just 'onLookJson'. An argument must always follow the :, so a method that doesn't take any arguments must not have one.
Ex
- (NSString *)fullName { .. }
This is an instance method, for example of a Person Class, you would call it like:-
NSString *theName = [aPerson fullName];
So
a method name that takes no
arguments is like 'speak'
a method
name that takes 1 argument is like
'speakTo:'
a method name that takes 2
arguments is like 'speakTo: language:'
a method name that takes 3
arguments is like 'speakTo: language: volume:'
etc.
All that is left is to put in the argument types and names.
Your function definition:
NSString *getKeyvalue( NSString *s, NSString *key ){
would become..
- (NSString *)getValue:(NSString *)s key:(NSString *)key { .. }
again, you need to declare it in the header or you will get a compiler warning.
- (NSString *)getValue:(NSString *)s key:(NSString *)key;
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.