ios - uiviewcontroller dealloc时如何在 objective-c 中触发 block 事件

Question

当 UIViewController dealloc 时，如何在 Objective C 中触发 block 事件。

例如:

   [PGMemberObj requestWithUserName:@"ab" andPassword:@"cc" andCallback:^(BOOL isSuc){
        if (isSuc) {
            NSLog("Login Suc.");
        }else
        {
            NSLog("Login Failed");
        }
    }];

当我弹出 ViewController 并执行 dealloc 时，我仍然收到 Login Suc。或登录失败消息。如何避免这个问题？

Answer 1

试试下面的代码:

__weak UIViewController *weakSelf = self;
[PGMemberObj requestWithUserName:@"ab" andPassword:@"cc" andCallback:^(BOOL isSuc){
    if ([weakSelf isViewLoaded] && [weakSelf.view window]) 
        //The view controller still exists AND it's being shown on screen
    else
        //Either dealloc'd or not on screen anymore
 }];

它将测试您的 View Controller 是否仍然存在并且仍在屏幕上。如果您不关心它是否仍在屏幕上显示，只需检查 weakSelf。

if (weakSelf)
    //Still exists
else
    //dealloc'd