Question

我和朋友正在为iPhone创建一个纸牌游戏，在这个项目的早期阶段，我正在开发一个Deck课程和一个Card课程来跟上卡片。我想测试Deck类的shuffle方法，但是我无法在Deck类实例中显示卡的值。 Deck类有一个NSArray的Card对象，它有一个名为displayCard的方法，它使用控制台输出（printf或NSLog）显示值和套装。为了一次性显示Deck实例中的卡片，我使用了这个[deck makeObjectsPerformSelector:@selector(displayCard)]，其中deck是Deck类中的NSArray。在Deck类内部，控制台输出上不显示任何内容。但是在测试文件中，它运行得很好。这是创建自己的NSArray的测试文件：

#import <Foundation/Foundation.h>
#import "card.h"

int main (int argc, char** argv)
{
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
    Card* two = [[Card alloc] initValue:2 withSuit:'d'];
    Card* three = [[Card alloc] initValue:3 withSuit:'h'];
    Card* four = [[Card alloc] initValue:4 withSuit:'c'];
    NSArray* deck = [NSArray arrayWithObjects:two,three,four,nil];

    //Ok, what if we release the objects in the array before they're used?
    //I don't think this will work...
    [two release];
    [three release];
    [four release];
    //Ok, it works... I wonder how...

    //Hmm... how will this work?
    [deck makeObjectsPerformSelector:@selector(displayCard)];
    //Yay! It works fine!

    [pool release];

    return 0;
}

这很好用，所以我围绕这个想法创建了一个初始化器，一次创建了52个卡片对象，并使用deck = [deck arrayByAddingObject:newCard]将它们添加到NSArray中。真正的问题是我如何使用makeObjectsPerformSelector或之前/之后的东西？

Answer 1

将对象添加到数组时，它会将retainCount增加1。这就是为什么释放它不会释放对象的原因。该阵列是在自动释放状态下创建的。释放池时，它会释放阵列和所有对象。您必须明白释放不等于免费。它只是减少了retainCount。只有当retainCount变为零时才会释放它。所以在你的函数之外，你必须以某种方式保留对象。

Answer 2

如果您想要查看保留计数的实时和实际操作，请拨打以下内容：

int main (int argc, char** argv)
{
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];

    Card* two = [[Card alloc] initValue:2 withSuit:'d'];
    NSLog(@"Current retain count for the '2' Card: %ud", [two retainCount]);

    Card* three = [[Card alloc] initValue:3 withSuit:'h'];
    Card* four = [[Card alloc] initValue:4 withSuit:'c'];
    NSArray* deck = [NSArray arrayWithObjects:two,three,four,nil];

    NSLog(@"Current retain count for the '2' Card after array retains it: %ud", [two retainCount]);

    [two release];
    [three release];
    [four release];

    NSLog(@"Current retain count for the '2' Card after releasing instance: %ud", [two retainCount]);

    [deck makeObjectsPerformSelector:@selector(displayCard)];

    [deck release];
    NSLog(@"Current retain count for the '2' Card after releasing instances within 'deck' array: %ud", [two retainCount]);

    [pool release];

    return 0;
}

类内外的makeObjectsPerformSelector问题？

2 个答案: