代码块是否完全取代了委托? [英] Do code blocks completely replace delegates?
问题描述
现在 iphone/ipad 开发最终支持块，这些是否完全消除了对代理的需求，或者代理作为一个完整的接口实现仍然更干净，而块更适合单个任务?
Now that blocks are finally supported for iphone/ipad development, do these completely remove the need for delegates or are delegates still cleaner as a complete interface implementation while blocks are more appropriate for single tasks?
推荐答案
我一直在寻找这方面的官方文档，但还没有找到.基于对 iOS 5 中公开的新类以及对预先存在的类所做的添加的审查，我建议我的团队假定委托协议，但在存在 直接因果关系时提供块代替em> 在特定的调用和块的性能之间.
I've been searching for official documentation on this but have yet to find any. Based on reviewing the new classes exposed in iOS 5 and those additions made to pre-existing classes, I'm recommending to my team to presume a delegate protocol but to provide a block instead when there is a direct causal nexus between that specific call and performance of the block.
因此，根据经验，当需要进行持续通信时，委托协议是正确的，导致通信的操作是分散的，或者操作来自第三方来源.块主要与异步操作相关联，尤其是单次类.
So, as a rule of thumb, a delegate protocol is correct when there's a need for ongoing communication, the actions causing the communication are diffuse or the actions are emanating from a third source. Blocks are primarily associated with asynchronous actions and single-shot classes in particular.
所以，一些例子:
UIScrollViewDelegate 是正确的委托协议，因为 (i) 可能需要传达的内容范围很广；(ii) 他们可能需要在任何时间以任何顺序进行沟通；(iii) 他们将因受托人无法控制的原因进行沟通.
UIScrollViewDelegate is correctly a delegate protocol because (i) there's a wide range of things that may need to be communicated; (ii) they may need to be communicated in any order and at any time; and (iii) they will be communicated for reasons beyond the delegate's control.
NSURLConnection +sendAsynchronousRequest:queue:completionHandler: 正确地使用了一个块来传递结果，因为 (i) 只有一个结果要报告；(ii) 报告作为调用者采取的行动的直接后果返回.
NSURLConnection +sendAsynchronousRequest:queue:completionHandler: correctly takes a block to deliver results because (i) there's exactly one result to report; and (ii) the report comes back as a direct consequence of action taken by the caller.
这篇关于代码块是否完全取代了委托?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IT屋！
