使用NSDictionary碰撞錯誤 - Iphone SDK

Question

Im使用字典來保存一些值爲「1」的位置;

/* * * header * * */ 

NSDictionary *Mypoints; 

/* * * * * * * * */ 

-(void)myfunc: (float)y :(float)x{ 

    NSLog(@"%@",Mypoints); 

    NSNumber *one = [NSNumber numberWithInt:1]; 
    NSString *key = [[NSString alloc] initWithFormat:@"%f,%f",y,x]; 

    [Mypoints setObject:one forKey:key]; 

    //show the value 
    NSNumber *tempNum = [Mypoints objectForKey:key]; 
    int i = tempNum.intValue; 
    NSLog(@"Value: %i",i); 

    //print all 
    NSLog(@"%@",Mypoints); 

} 

我第一次調用這個函數一切正常，它會創建字典並在最後一行中打印「數組」。但是當我再次輸入這個函數時，它會崩潰而沒有錯誤。

我不知道什麼可能會發生......

我解決了崩潰做：

Mypoints = [[NSMutableDictionary dictionaryWithObject:one forKey:key]retain]; 

我解決了如何添加多個點：

//到viewDidLoad中

Mypoints = [[NSMutableDictionary alloc] init]; 

//進入MYFUNC

[Mypoints setObject:one forKey:key]; 

Answer 1

我的點沒有被保留。所以第一次它將是零，第二次Mypoints將指向已釋放的內存。在此代碼

其他小問題：

1. Mypoints應設置爲無使用前（我想這是在其他地方完成）。
2. Mypoints = [NSDictionary dictionaryWithObject：one forKey：key];您的字典也將只包含1個鍵/值對，因爲您每次都創建一個新的字典。 NSString * key = [[NSString alloc] initWithFormat：@「％f，％f」，y，x];這會泄漏，因爲它沒有被釋放。

---

 

// Not keen on this being a global but whatever... It needs to be initialised somewhere in this example. 
NSMutableDictionary* Mypoints = nil;
 

-(void)myfunc: (float)y :(float)x 
{
 
    // This is hacky but shows the principle. 
    if (Mypoints == nil) 
    { 
     Mypoints = [ NSMutableDictionary alloc ] initWithCapacity: 10 ]; 
     // Or whatever you think the size might be. Don't forget to release it somewhere. 
    }
 

NSNumber *one = [NSNumber numberWithInt:1]; 
NSString *key = [NSString stringWithFormat:@"%f,%f",y,x]; 
// This stops the leak since it is now already autoreleased. 

[ MyPoints setObject: one forKey: key ]; // Be careful no other key can have the same x and y value. 

//show the value 
NSNumber *tempNum = [Mypoints objectForKey:key]; 
int i = tempNum.intValue; 
NSLog(@"Value: %i",i); 

//print all 
NSLog(@"%@",Mypoints); 

}

Answer 2

因爲[NSDictionary dictionaryWithObject:one forKey:key]會返回一個自動釋放對象，該對象在調用-myfunc:之間的某個時間釋放。 NSLog（）在第一行顯然發生了崩潰。