多线程和自动释放池

本文介绍了多线程和自动释放池的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 当我掌握我的技能与多线程与GCD，我遇到一些问题。假设你有以下方法： - （void）方法{ NSString * string = [NSString string]; //将被自动释放 dispatch_async（dispatch_get_global_queue（DISPATCH_QUEUE_PRIORITY_DEFAULT，0），^ { //非常非常冗长的操作... NSLog （@％@，string）; //是安全吗？}）; } 我想知道这是否正确，因为我认为我应该保留在块执行之前的字符串：事实上我担心事件循环完成并发送 string 一个autorelease消息，然后使用 string 在块中。这将导致程序崩溃。 我是对吗？是否应该向 string 发送一个retain和一个释放消息，或者这是正确的实现？ 提前感谢！解决方案 不要害怕： 块捕获了周围方法/函数的范围，因为它会自动保留变量，在块内使用。注意，当你在块中使用 self 时，这可能会极大地影响对象的生命周期！ 此规则有一个例外，它们是声明为的变量 __ block SomeObjectPointerType variableName 更新 因为这个答案有新的评论在ARC下所有对象变量默认为 __ strong ，并且在ARC下引入了一些变化： 这也适用于标有 __ block 的变量。如果你想避免强制捕获块中的变量，你应该定义一个局部变量 __ weak 。 End Update 如果你想了解更多关于块的信息，bbum给了一个很好的会话，叫做 介绍块和大中央调度在iPhone上 （iTunes U链接）在WWDC 2010。 块详细信息部分始于11:30。 As I'm mastering my skills with multithreading with GCD, I've come across some question. Suppose you have the following method: - (void)method { NSString *string= [NSString string]; //will be autoreleased dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //very very lengthy operation... NSLog(@"%@", string); //is it safe? });}I'm wondering if this is correct, because I think I should have retained string before the block execution: in fact I fear that the event loop finishes and sends string an autorelease message before using string in the block. That would crash the program.Am I right? Should I send a retain and a release message to string or this is the correct implementation?Thanks in advance! 解决方案 Fear not:A block captures the scope of the surrounding method/function in that it automatically retains any object-variable that is used inside of the block. Be aware of that when you use self inside of a block, as this may greatly affect the lifetime of the object!There is one exception to this rule, and that are variables declared as__block SomeObjectPointerType variableNameUpdateBecause there’s a new comment on this answer, I should probably add that things changed a little with the introduction of ARC:Under ARC all object variables default to __strong, and this holds for variables marked with __block as well. If you want to avoid strong capturing of a variable in a block, you should define a local variable that is __weak.End UpdateIf you like to learn more about blocks, bbum gave an excellent session called Introducing Blocks and Grand Central Dispatch on iPhone (iTunes U link) at WWDC 2010.The "Block Details" section starts at 11:30. 这篇关于多线程和自动释放池的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！