objective-c-blocks | 易学教程

How to use NSComparator?

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I would like to know if the below question is possible using NSComparator or not? I have two arrays; both hold data models. I have a property named rank in the data model. Now I want to compare both arrays and want to know if one of them holds higher ranked data models. If Yes I would like to get NSComparisonResult = NSOrderedAscending . By the way I'm using another approach here: is "total of each data Model's rank in array and if the total is greater than second array's data Model's total rank." Samuel Goodwin Yes, it would look something like this: NSArray *someArray = /* however you get an

iOS 5 Twitter Framework & completionHandler block - “Capturing 'self' strongly in this block is likely to lead to a retain cycle”

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I am very new to programming and Objective-C and I am trying to work out what is wrong with my code. I have read a bit about blocks but I don't know how any of what I have read so far is relevant to my code. My code is using the iOS 5 Twitter Framework. I use most of the sample code that Apple provides so I actually had no clue at first that I was using a block for the completion handler. Now I get those two messages from Xcode 4 saying " 1. Block will be retained by an object strongly retained by the captured object " and " Capturing 'self' strongly in this block is likely to lead to a retain

Referencing an NSOperation object in its own completion block with ARC

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问题 I'm having difficulty converting some NSOperation code to ARC. My operation object uses a completion block, which in turn contains a GCD block that updates the UI on the main thread. Because I reference my operation object from inside its own completion block, I'm using a __weak pointer to avoid a memory leak. However, the pointer is already set to nil by the time my code runs. I've narrowed it down to this code sample. Anyone know where I went wrong, and the right way to accomplish this?

ObjectiveC and JavaScriptCore: Will using this method of calling CallBacks cause memory issues?

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问题 DISCLAIMER: This is a long post, but could prove very valuable for those grappling with using the new ObjectiveC JavascriptCore framework and doing asynchronous coding between ObjC and JS. Hi there, I'm super new to Objective C and am integrating a javascript communication library into my iOS app. Anyway, I've been trying my hand at using the new ObjectiveC JavaScriptCore Framework introduced in iOS7. It's pretty awesome for the most part, though quite poorly documented so far. It's really

Blocks vs Delegates [duplicate]

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问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Do code blocks completely replace delegates? I just encountered the following declaration from a forum: "Delegates is the past. Blocks are the future." 1) Are blocks the preferred way to do 'delegation' duties over delegates? 2) Is there any particular benefit of using a delegate vs a block? 回答1: I think there's a slight misunderstanding in what delegates do and what blocks do. In Objective-C, there are three

iOS autorelease pool blocks

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问题 I was reading the documentation from apple about memory management when I got to autorelease pool blocks and something got me thinking. Any object sent an autorelease message inside the autorelease pool block is released at the end of the block. I am not sure I fully understand this. Any object created inside an autorelease pool block gets released at the end of the block anyway because that is it's life span. Why would you need to call autorelease to the object when it is going to get

NSComparisonResult and NSComparator - what are they?

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What is NSComparisonResult and NSComparator ? I've seen one of the type definitions, something like that: typedef NSComparisonResult (^NSComparator)(id obj1, id obj2); Is it any different from a function pointer? Also, I can't even guess what the ^ symbol means. ^ signifies a block type , similar in concept to a function pointer. typedef NSComparisonResult (^NSComparator)(id obj1, id obj2); // ^ ^ ^ // return type of block type name arguments This means that the type NSComparator is a block that takes in two objects of type id called obj1 and obj2 , and returns an NSComparisonResult .

Selectors or Blocks for callbacks in an Objective-C library

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问题 Question We're developing a custom EventEmitter inspired message system in Objective-C. For listeners to provide callbacks, should we require blocks or selectors and why? Which would you rather use, as a developer consuming a third party library? Which seems most in line with Apple's trajectory, guidelines and practices? Background We're developing a brand new iOS SDK in Objective-C which other third parties will use to embed functionality into their app. A big part of our SDK will require

Are Objective-C blocks autoreleased?

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If I declare a block like this ^{ DoSomething; } and put it in an instance variable, do I need to Block_copy() if I'm going to keep it around? Yes, you need to copy. Not because they are autoreleased, but because they start on the stack. Note that blocks also behave like regular Objective-C objects, so that you can copy them using the regular copy message: void storeBlockForLater: (dispatch_block_t) block { [someArray addObject:[[block copy] autorelease]]; } Or, if you have a block property: @property(copy) dispatch_block_t block; Retaining does not help here. 来源： https://stackoverflow.com

Chain UIView animations with time intervals

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I need to animate 3 UIViews (fade in/out). 1 animation duration is 0.6s (fade in/out cycle is 0.6+0.6s). But I need to launch animations in 0.2 seconds. 1st animation should be launched in 0.0 seconds. 2nd animation should be launched in 0.2 seconds. 3rd animation should be launched in 0.4 seconds. And all of them should be looped "indefinitely" (until some trigger). What I have at the moment: - (void)playAnimation { isAnimated = YES; [self animateView:firstView afterDelay:0.0]; [self animateView:secondView afterDelay:0.2]; [self animateView:thirdView afterDelay:0.4]; } - (void)stopAnimation {