Say I have a NSViewController which will be displayed in a popover using something similar to this:
- (void) createAndShowPopover
{
TargetViewController * targetViewContoller = [[TargetViewController alloc] init];
NSPopover * targetPopover = [[NSPopover alloc] init];
targetPopover.contentViewController = targetViewContoller;
targetPopover.delegate = self;
[targetPopover setAppearance: NSPopoverAppearanceMinimal];
[targetPopover setAnimates: NO];
[targetPopover setBehavior: NSPopoverBehaviorTransient];
[targetPopover showRelativeToRect: ...];
}
Now TargetViewContoller contains a NSTextView and NSButton. When the button is clicked, I would like the parent controller (the view controller which owns targetPopover) to perform an action based on the contents of targetViews textView, then close the popover.
There are three ways I can think of doing this.
A block property on targetViewController such as typedef void (^TextRestoreBlock) (NSString * textToRestore); and adding the following code to the createAndShowPopover code:
__unsafe_unretained typeof(self) weakSelf = self;
targetController.restoreBlock =
^(NSString * textToRestore)
{
// Establish the strong self reference
__strong typeof(self) strongSelf = weakSelf;
[strongSelf.textView setString: textToRestore];
[strongSelf.targetPopover close];
}; // Set our string
Using a delegate and instead having createAndShowPopover add:
targetController.restoreDelegate = self;
And adding the code from the previous block to a delegate method.
I think I much prefer method #2 (delegate) as it seems neater. My overall question would be, is there a preferred style? Have I missed the mark completely?
Note that in my specific case, this is for mac development, but I believe the same concept would apply to iOS and uipopovercontroller.
I agree method #2 has always worked for me. Although there aren't any overwhelming computational benefits to doing one or the other. #2 is cleaner and a bit easier to edit if you decide to add more functionality. Go for it.
Related
I'd like to display some data of my model within a status bar menu. So, I bound my entity-object to the title of an NSMenuItem:
[self.statusMenu setAutoenablesItems:NO];
NSMenuItem * exportMenuItem = [[NSMenuItem alloc] init];
[exportMenuItem bind:#"title" toObject:expo withKeyPath:#"menuItemTitle" options:nil];
[exportMenuItem setEnabled:NO];
[self.statusMenu insertItem:exportMenuItem atIndex:3];
It works fine so far from init. But when I update my Model it does not updates the title of the NSMenuItem.
For reference, the canonical solution to this issue is to implement a class method like this:
+ (NSSet *)keyPathsForValuesAffectingMenuItemTitle
{
return [NSSet setWithObjects: #"propertyMenuItemTitleDependsOn1",
#"propertyMenuItemTitleDependsOn2",
nil];
}
If you implement a method like this, then the framework will handle calling willChangeValueForKey: and didChangeValueForKey: for the key menuItemTitle any time any of the other properties are changed.
Okay I got it:
menuItemTitle is a dynamic getter method which combines two actual properties of expo. So the reason for NSMenuItem's title to not get updated is probably, that menuItemTitle probably never gets actually set.
So how do I tell, that menuItemTitle was changed, when one of my properties was set?
Overriding expo's setters to add [self willChangeValueForKey:#"menuItemTitle"]; and [self didChangeValueForKey:#"menuItemTitle"]; does not work as it causes an endless loop in calling the setter itself again and again.
So here is my solution: I overrode [NSManagedObject setValue:(id)value forKey:(NSString *)key]:
- (void)setValue:(id)value forKey:(NSString *)key {
[self willChangeValueForKey:#"menuItemTitle"];
[super setValue:value forKey:key];
[self didChangeValueForKey:#"menuItemTitle"];
}
I am writing an app which is a sort of dictionary - it presents the user with a list of terms, and when clicked on, pops up a dialog box containing the definition. The definition itself may also contain terms, which in turn the user can click on to launch another definition popup.
My main app is stored in 'myViewController.m'. It calls a custom UIView class, 'CustomUIView.m' to display the definition (this is the dialog box that pops up). This all works fine.
The text links from the CustomUIView then should be able to launch more definitions. When text is tapped in my CustomUIView, it launches another CustomUIView. The problem is, that this new CustomUIView doesn't have access to the hash map which contains all my dictionary's terms and definitions; this is only available to my main app, 'myViewController.m'.
Somehow, I need to make my hash map, dictionaryHashMap, visible to every instance of the CustomUIView class. dictionaryHashMap is created in myViewController.m when the app opens and doesn't change thereafter.
I don't wish to limit the number of CustomUIViews that can be opened at the same time (I have my reasons for doing this!), so it would be a little resource intensive to send a copy of the dictionaryHashMap to every instance of the CustomUIView. Presumably, the solution is to make dictionaryHashMap a global variable.
Some of my code:
From myViewController.m:
- (void)viewDidLoad
{
self.dictionaryHashMap = [[NSMutableDictionary alloc] init]; // initialise the dictionary hash map
//... {Code to populate dictionaryHashMap}
}
// Method to pop up a definition dialog
- (void)displayDefinition:(NSString *) term
{
NSArray* definition = [self.dictionaryHashMap objectForKey:term]; // get the definition that corresponds to the term
CustomUIView* definitionPopup = [[[CustomUIView alloc] init] autorelease]; // initialise a custom popup
[definitionPopup setTitle: term];
[definitionPopup setMessage: definition];
[definitionPopup show];
}
// Delegation for sending URL presses in CustomUIView to popupDefinition
#pragma mark - CustomUIViewDelegate
+ (void)termTextClickedOn:(CustomUIView *)customView didSelectTerm:(NSString *)term
{
myViewController *t = [[myViewController alloc] init]; // TODO: This instance has no idea what the NSDictionary is
[t displayDefinition:term];
}
From CustomUIView.m:
// Intercept clicks on links in UIWebView object
- (BOOL)webView: (UIWebView*)webView shouldStartLoadWithRequest: (NSURLRequest*)request navigationType: (UIWebViewNavigationType)navigationType {
if ( navigationType == UIWebViewNavigationTypeLinkClicked ) {
[myViewController termTextClickedOn:self didSelectTerm:request];
return NO;
}
return YES;
}
Any tips on how to make the dictionaryHashMap visible to CustomUIView would be much appreciated.
I have tried making the dictionaryHashMap global by doing the following:
Changing all instances of 'self.dictionaryHashMap' to 'dictionaryHashMap'
Adding the line 'extern NSMutableDictionary *dictionaryHashMap;' to CustomUIView.h
Adding the following outside of my implementation in myViewController.m: 'NSMutableDictionary *dictionaryHashMap = nil;'
However, the dictionaryHashMap remains invisible to CustomUIView. As far as I can tell, it actually remains a variable which is local to myViewController...
It's not resource-intensive to pass around the reference (pointer) to dictionaryHashMap. A pointer to an object is only 4 bytes. You could just pass it from your view controller to your view.
But I don't know why you even need to do that. Your view is sending a message (termTextClickedOn:didSelectTerm:) to the view controller when a term is clicked. And the view controller already has a reference to the dictionary, so it can handle the lookup. Why does the view also need a reference to the dictionary?
Anyway, if you want to make the dictionary a global, it would be more appropriate to initialize it in your app delegate, in application:didFinishLaunchingWithOptions:. You could even make the dictionary be a property of your app delegate and initialize it lazily.
UPDATE
I didn't notice until your comment that termTextClickedOn:didSelectTerm: is a class method. I assumed it was an instance method because myViewController starts with a lower-case letter, and the convention in iOS programming is that classes start with capital letters. (You make it easier to get good help when you follow the conventions!)
Here's what I'd recommend. First, rename myViewController to MyViewController (or better, DefinitionViewController).
Give it a property that references the dictionary. Whatever code creates a new instance of MyViewController is responsible for setting this property.
Give CustomUIView properties for a target and an action:
#property (nonatomic, weak) id target;
#property (nonatomic) SEL action;
Set those properties when you create the view:
- (void)displayDefinition:(NSString *)term {
NSArray* definition = [self.dictionaryHashMap objectForKey:term];
CustomUIView* definitionPopup = [[[CustomUIView alloc] init] autorelease]; // initialise a custom popup
definitionPopup.target = self;
definitionPopup.action = #selector(termWasClicked:);
...
In the view's webView:shouldStartLoadWithRequest: method, extract the term from the URL request and send it to the target/action:
- (BOOL)webView: (UIWebView*)webView shouldStartLoadWithRequest: (NSURLRequest*)request navigationType: (UIWebViewNavigationType)navigationType {
if ( navigationType == UIWebViewNavigationTypeLinkClicked ) {
NSString *term = termForURLRequest(request);
[self.target performSelector:self.action withObject:term];
return NO;
}
return YES;
}
In the view controller's termWasClicked: method, create the new view controller and set its dictionary property:
- (void)termWasClicked:(NSString *)term {
MyViewController *t = [[MyViewController alloc] init];
t.dictionary = self.dictionary;
[t displayDefinition:term];
}
Create a class that will be used as singleton. Example.
You Should always keep your data in separate class as the mvc pattern suggest and that could be achieved by using a singleton class for all your dictionary terms and accesing them from every custom view when needed.
I'm seeing some disturbing irregularities concerning object allocation and initialization in an app I'm trying to write.
I have a 'root' Modelcontroller object, which in turn contains references to subcontrollers. The root controller is called modelController, and in it's init method it allocates and inits the subcontrollers like so:
- (id)init
{
NSLog(#"%#", #"ModelController begin init");
self = [super init];
if (self) {
LibraryController * tempLibrary = [[LibraryController alloc] init];
self.library = tempLibrary;
StoresController * tempStores = [[StoresController alloc] init];
self.stores = tempStores;
CLLocationManager * tempLocationManager = [[CLLocationManager alloc] init];
self.locationManager = tempLocationManager;
}
NSLog(#"%#", #"ModelController complete init");
return self;
}
Pretty standard. The subcontrollers' init code also contain an NSLog messages at the beginning and the end, for me to be able to see that all is well.
The properties are defined as
#property (strong) LibraryController * library;
#property (strong) StoresController * stores;
#property (strong) CLLocationManager * locationManager;
And I am using ARC.
What puzzles me is that sometimes I see the NSLogs from one of the subcontrollers, but not from the root controller. Sometimes I see the 'begin init' log message from the root controller, but not the 'complete init'. Sometimes I see no init log messages. The application launches anyway in any of these cases.
This happens seemingly at random, in one out of five launches or in one out of twenty launches. When it happens, the app acts very strange (but not every time, mind you), beachballing for no apparent reason and exhibiting general wonkiness.
As a side note, at one time I put a breakpoint in the init method of the StoreController class, which when pausing executing spit out a chunk of random data in the debugging console:
$m2303,3503,3603,3703,3803,3903#00$m2303,3503,3603,3a03#00$88ee410901000000981e420901000000001e42090100000060ee410901000000b062f668ff7f000070044391ff7f0000f00e0800000000000300000068200100dc62f668ff7f0000d862f668ff7f00000000000000000000717ddd8aff7f00000000000068200100801e420901000000000000000600000706000007000000007063f668ff7f000003280000000000007863f668ff7f000001ee410901000000f062f668ff7f00006c5bd391ff7f000000000000ff7f0000ab064391ff7f000000000000ffffffff032800000000000040
...and so on
Where should I begin to look to troubleshoot this?
The modelController is alloc init'd from the MyDocument equivalent class, and is modeled as a singleton.
The singleton implementation looks like this:
static ModelController *sharedModelController = nil;
+ (ModelController*)sharedManager
{
if (sharedModelController == nil) {
sharedModelController = [self new];
}
return sharedModelController;
}
Final note: I have tried removing the locationManager stuff and disabling/enabling the 'Restore state' preference in the scheme, but to no avail.
Sounds like you're doing some UI stuff not on the main thread.
This generally leads to weird behavior.
Make sure you call everything UI related on the main thread
Best guess: the ModelController object is being released. Perhaps the Singleton is faulty.
I often do something like:
CoolViewController *coolViewController = [[CoolViewController alloc] init];
[self.navigationController pushViewController:coolViewController animated:YES];
[coolViewController release];
How would I, in a category of UINavigationController, override forwardInvocation: so that I could just instead do:
[self.navigationController pushCoolViewControllerAnimated:YES];
Please include the relevant code in your answer, not just an explanation. Thank you!
Feel free to comment on whether this is good practice. I'm also asking this for educational purposes, but it seems to me that in this case, the simplification in code may outweight the unnoticeable (correct?) cost in processing time & memory usage. Also, I come from a Ruby background and love to use dynamic programming to simplify things, e.g., dynamic finders (e.g., find_by_name) in Rails.
Bonus points if you could implement pushCoolViewControllerAnimated:withBlock and invoke the block after initializing the view controller, allowing me to set certain instance variables on the view controller created.
UPDATE: I just remembered that ARC is coming soon. So this specific example may not be so helpful then, but still a great exercise/example that could be used in other cases, e.g., dynamic finders for Core Data & passing a block to configure the NSFetchRequest.
Use the dynamic method resolution mechanism described in the Objective-C Runtime Programming Guide, specifically, +[NSObject resolveInstanceMethod:]:
#implementation UINavigationController (FWD)
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
NSString *name = NSStringFromSelector(sel);
NSString *prefix = #"push";
NSString *suffix = #"Animated:";
if ([name hasPrefix:prefix] && [name hasSuffix:suffix]) {
NSRange classNameRange = {[prefix length],
[name length] - [prefix length] - [suffix length]}
NSString *className = [name substringWithRange:classNameRange];
Class cls = NSClassFromString(className);
if (cls) {
IMP imp = imp_implementationWithBlock(
^(id me, BOOL animated) {
id vc = [[cls alloc] init];
[me pushViewController:vc animated:animated];
[vc release];
});
class_addMethod(cls, sel, imp, "v#:c");
return YES;
}
}
return [super resolveInstanceMethod:sel];
}
#end
Of course, if UINavigationController already uses +resolveInstanceMethod:, you've now broken it. Doing this in a subclass of UINavigationController, or using method swizzling to enable invoking the original implementation, would solve that problem.
The version accepting a post-creation block is a straightforward extension (change the block parameters, change the type encoding, change the selector name pattern and how you extract the intended class name).
I've just run into blocks and I think they are just what I'm looking for, except for one thing: is it possible to call a method [self methodName] from within a block?
This is what I'm trying to do:
-(void)someFunction{
Fader* fader = [[Fader alloc]init];
void (^tempFunction)(void) = ^ {
[self changeWindow:game];
//changeWindow function is located in superclass
};
[fader setFunction:tempFunction];
}
I've been searching for a couple of days and I can't find any evidence that this is possible.
Is this at all possible, or am I trying to use blocks for something they aren't meant for?
The reason I'm using blocks is that I've created a Fader class, and I want to store a block for it to execute when it finishes fading out.
Thank you
EDIT:
Okay, I added in the suggestion, but I'm still getting an EXC_BAD_ACCESS error...
-(void)someFunction{
Fader* fader = [[Fader alloc]init];
__block MyScreen* me = self;
void (^tempFunction)(void) = ^ {
[me changeWindow:game];
//changeWindow function is located in superclass
};
[fader setFunction:tempFunction];
[fader release];
}
Maybe I'm not allowed to give fader the function...?
Yes, you can do this.
Note, however, that the block will retain self. If you end up storing this block in an ivar, you could easily create a retain cycle, which means neither would ever get deallocated.
To get around this, you can do:
- (void) someMethodWithAParameter:(id)aParameter {
__block MySelfType *blocksafeSelf = self;
void (^tempFunction)(void) = ^ {
[blocksafeSelf changeWindow:game];
};
[self doSomethingWithBlock:tempFunction];
}
The __block keyword means (among other things) that the referenced object will not be retained.
The accepted answer is outdated. Using __block in that case can cause errors!
To avoid this problem, it’s best practice to capture a weak reference to self, like this:
- (void)configureBlock {
XYZBlockKeeper * __weak weakSelf = self;
self.block = ^{
[weakSelf doSomething]; // capture the weak reference
// to avoid the reference cycle
}
}
Please, look at Apple Documentation - Avoid Strong Reference Cycles when Capturing self
for more details.
__block CURRENTViewController *blocksafeSelf = self;
[homeHelper setRestAsCheckIn:strRestId :^(NSObject *temp) {
[blocksafeSelf YOURMETHOD:params];
}];
Is it possible to call a method [self methodName] from within a block?
Yes, why not. If your tempFunction is an instance method, you can do it. The called method should be accessible is the only restriction.
Consider this (which I think is the best practice)
#implementaion ViewController
- (void) viewDidLoad {
__weak typeof(self) wself = self;
[xxx doSomethingUsingBlock: ^{
__strong typeof(wself) self = wself;
[self anotherMessage];
}];
}
#end
Moreover, You can define wrapper macros.
#define MakeWeakSelf __weak typeof(self) wself = self
#define MakeStrongSelf __strong typeof(wself) self = wself
I wonder whether you [fader setFunction:tempFunction]; then is synchronous or asynchronous.
blocks push onto stack.so in MRR,if you don't retain it,it will pop off.
-(void)someFunction{
Fader* fader = [[Fader alloc]init];
void (^tempFunction)(void) = ^ {
[self changeWindow:game];
//changeWindow function is located in superclass
};
[fader setFunction:tempFunction];
//if the tempFunction execute there will be right.
}//there the tempFunction pop off
//....some thing go on
//execute the tempFunction will go wrong.