block | 易学教程

generateCGImagesAsynchronouslyForTimes in ARC

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问题 If I run the following in a project where ARC is enabled the completion handler never fires. But without ARC it works as expected. What am I missing here? NSURL *url = [NSURL URLWithString:@"http://media.w3.org/2010/05/sintel/trailer.mp4"]; AVURLAsset *asset=[[AVURLAsset alloc] initWithURL:url options:nil]; AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset]; generator.appliesPreferredTrackTransform = YES; CMTime thumbTime = CMTimeMakeWithSeconds(5,30);

Producer consumer implementation in a block device driver?

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I'm trying to implement a producer-consumer like situation in my block level driver (on linux kernel version 2.6.39.1). My block driver's make_request_fn receives a stream of struct bio from a userlevel application. On receiving these BIOs, they are queued up. Next, I create a new struct bio which will hold all the information present in the queued BIOs. This new "merged_bio" will be submitted only if there is a struct request slot available in the lower level driver's request_queue . In the meantime, my block driver will continue to receive BIOs from the userlevel application and will queue

Do standalone JavaScript blocks have any use?

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问题 The MDN article on JavaScript blocks gives this example: var x = 1; { var x = 2; } alert(x); // outputs 2 As you can see JavaScript doesn't have block scope. So are there any good use cases for standalone blocks in JavaScript? By "standalone" I mean not paired with a control flow statement ( if , for , while , etc.) or a function . 回答1: Short answer: ...not really. The only use I know for them is labels: myBlock: { // stuff if (something) break myBlock // jump to end of block // more stuff if

js图片轮播（翻页切换）

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前面已经介绍了两种常见的图片轮播样式，今天将介绍一种更为常见的图片轮播形式，和淘宝的功能样式类似，这三种轮播基本上涵盖了常见网站图片轮播的所有类型，难度的话，个人认为淡入淡出是比较难的，但只要用心，仔细的体会核心思想，一步步来，相信还是可以很好地掌握的！ <!DOCTYPE html> <html lang="en">  <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>图片轮播</title>  <style> .all { width: 700px; height: 400px; position: relative; overflow: hidden; margin: 0 auto; } .block { width: 700px; height:

Visual block edit in vim

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问题 I have refer to this post to use block editing in vim. But when I key I or c after the block select, vim enters the normal edit mode just as if I pressed a i . I also found, when block is selected, I can use the x key to delete chars in the block. Before press I : After press I : How can I block input chars? the +visualextra have enabled from below version info. > $ vim --version VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Jan 2 > 2014 19:39:47) Included patches: 1-52 Modified by > pkg-vim

static关键字

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版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。本文链接：https://blog.csdn.net/luoyoub/article/details/82874993 ———————————————— 版权声明：本文为CSDN博主「忧伤的比目鱼」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。原文链接：https://blog.csdn.net/luoyoub/article/details/82874993 以下情况会触发类的初始化：遇到new，getstatic，putstatic，invokestatic这4条指令；使用java.lang.reflect包的方法对类进行反射调用；初始化一个类的时候，如果发现其父类没有进行过初始化，则先初始化其父类（注意！如果其父类是接口的话，则不要求初始化父类）；当虚拟机启动时，用户需要指定一个要执行的主类（包含main方法的那个类），虚拟机会先初始化这个主类；当使用jdk1.7的动态语言支持时，如果一个java.lang.invoke.MethodHandle实例最后的解析结果REF_getstatic，REF_putstatic,REF_invokeStatic的方法句柄，并且这个方法句柄所对应的类没有进行过初始化

How to pass a block to another in Ruby?

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问题 Assuming I have the following proc: a = Proc.new do puts "start" yield puts "end" end Also assuming I pass a to another method which subsequently calls instance_eval on another class with that block, how can I now pass a block onto the end of that method which gets yielded in a . For example: def do_something(a,&b) AnotherClass.instance_eval(&a) # how can I pass b to a here? end a = Proc.new do puts "start" yield puts "end" end do_something(a) do puts "this block is b!" end Output should of

smalltalk block - can I explicitly set the returning value and stop executing the block?

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The return value of #value: message, when sent to a block, is the value of the last sentence in that block. So [ 1 + 2. 3 + 4. ] value evaluates to 7. I find that hard to use sometimes. Is there a way to explicitly set the returning value and stop executing the block? For exercise, try rewriting this block without using my imaginary #return: message and see how ugly it gets. I must be missing something. [ :one :two | one isNil ifTrue: [ two isNil ifTrue: [ self return: nil ] ifFalse: [ self return: true ] ]. two ifNil: [ self return: false ]. (one > two) ifTrue: [ self return: true ] ifFalse:

Reference the invoking object in the passed block in Ruby

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Is there any way to get hold of the invoked object inside the block thats being called. For instance, is there any way for the blocks to get access to the scope of the method batman or the class SuperHeros class SuperHeros attr_accessor :news def initialize @news = [] end def batman task puts "Batman: #{task} - done" yield "feed cat" @news << task end end cat_woman = lambda do |task| puts "Cat Woman: #{task} - done" # invoker.news << task end robin = lambda do |task| puts "Robin: #{task} - done" # invoker.news << task end characters = SuperHeros.new characters.batman("kick Joker's ass", &cat

Jade - Using Block inside script tag

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问题 Hi there I'm trying using Jade's blocks and extends for a node.js project, and the ideia is to have something like this: layout.jade: head script $(document).ready(function() { block js_doc_ready //here goes the doc ready }); index.jade: block js_doc_ready alert('hello!'); alert('one more js line code'); alert('end my js doc ready for this view'); This would give me a index.html like this: ... <head> <script type="text/javascript"> $(document).ready(function() { alert('hello!'); alert('one