循環，直到條件達到iPhone

Question

我有後按下按鈕，我想一個循環運行，直至達到條件這裏有一個問題...

：

- (IBAction)buttonclick1 ... 

if ((value2ForIf - valueForIf) >= 3) { ... 

我想一個循環運行至

((value2ForIf - valueForIf) >= 3) 

然後執行與IF語句相關的代碼。

我打算實現的是在繼續執行代碼之前，繼續檢查上述語句是否爲真的程序。除此之外，在IF之下還有一個else語句，但我不知道這是否會影響循環。

我不確定這裏所需的循環格式，我試過的所有東西都會導致錯誤。任何幫助將不勝感激。

斯圖

Answer 1

- (IBAction)buttonclick1 ... 
{ 
    //You may also want to consider adding a visual cue that work is being done if it might 
    //take a while until the condition that you're testing becomes valid. 
    //If so, uncomment and implement the following: 

    /* 
    //Adds a progress view, note that it must be declared outside this method, to be able to 
    //access it later, in order for it to be removed 
    progView = [[MyProgressView alloc] initWithFrame: CGRectMake(...)]; 
    [self.view addSubview: progView]; 
    [progView release]; 

    //Disables the button to prevent further touches until the condition is met, 
    //and makes it a bit transparent, to visually indicate its disabled state 
    thisButton.enabled = NO; 
    thisButton.alpha = 0.5; 
    */ 

    //Starts a timer to perform the verification 
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval: 0.2 
          target: self 
          selector: @selector(buttonAction:) 
          userInfo: nil 
          repeats: YES]; 
} 


- (void)buttonAction: (NSTimer *) timer 
{ 
    if ((value2ForIf - valueForIf) >= 3) 
    { 
    //If the condition is met, the timer is invalidated, in order not to fire again 
    [timer invalidate]; 

    //If you considered adding a visual cue, now it's time to remove it 
    /* 
     //Remove the progress view 
     [progView removeFromSuperview]; 

     //Enable the button and make it opaque, to signal that 
     //it's again ready to be touched 
     thisButton.enabled = YES; 
     thisButton.alpha = 1.0; 
    */ 

    //The rest of your code here: 
    } 
} 

Answer 2

而不是運行一個緊密的循環，這將阻止在另一個線程的應用程序的執行，除非運行，你可以使用一個NSTimer在自己選擇的時間間隔來調用一個方法，並檢查條件在方法。如果條件滿足，您可以使計時器無效並繼續。

Answer 3

從你說什麼，你想要的是一個while循環

while((value2ForIf - valueForIf) < 3) { ...Code Here... } 

這隻要值差小於3運行在括號中的代碼，這意味着它將運行，直到它們的區別是3或更大。但正如Jasarien所說。這是一個壞主意，因爲你會阻止你的程序。如果值正在被代碼本身更新，那很好。但是，如果它們由用戶的某個用戶界面進行更新，則while循環會阻止用戶界面，並且不允許用戶輸入任何內容。