使用NSDictionary碰撞错误 - Iphone SDK

Question

Im使用字典来保存一些值为“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); 

} 

我第一次调用这个函数一切正常，它会创建字典并在最后一行中打印“数组”。但是当我再次输入这个函数时，它会崩溃而没有错误。

我不知道什么可能会发生......

我解决了崩溃做：

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

我解决了如何添加多个点：

//到viewDidLoad中

Mypoints = [[NSMutableDictionary alloc] init]; 

//进入MYFUNC

[Mypoints setObject:one forKey:key]; 

Answer 1

我的点没有被保留。所以第一次它将是零，第二次Mypoints将指向已释放的内存。在此代码

其他小问题：

1. Mypoints应设置为无使用前（我想这是在其他地方完成）。
2. Mypoints = [NSDictionary dictionaryWithObject：one forKey：key];您的字典也将只包含1个键/值对，因为您每次都创建一个新的字典。 NSString * key = [[NSString alloc] initWithFormat：@“％f，％f”，y，x];这会泄漏，因为它没有被释放。

---

 

// 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

因为[NSDictionary dictionaryWithObject:one forKey:key]会返回一个自动释放对象，该对象在调用-myfunc:之间的某个时间释放。 NSLog（）在第一行显然发生了崩溃。