关于 NSString 的一个重要问题

Question

问题是在我按下 2 个按钮后，应用程序崩溃了，我不知道为什么

Button1 连接到 button1 Button2 连接到 button2 ... Button5 连接到 button5

我做错了什么？

基本上我想检查#的序列是否正确打入（55235）

在我的 AppDelegate.H 文件中，我定义了一个名为

的变量

NSString* myEasterEgg;

在 AppDelegate.M 中，我有 5 个正确连接的按钮，每个按钮都有自己的方法

-(IBAction)button1:(id)sender
{
if(CFStringCompare((CFStringRef)myEasterEgg, (CFStringRef)@"52235", 1) == 0)
{
myEasterEgg = @"";
} else {
myEasterEgg = [myEasterEgg stringByAppendingString:@"1"];
}
}

-(IBAction)button2:(id)sender
{
if(CFStringCompare((CFStringRef)myEasterEgg, (CFStringRef)@"52235", 1) == 0)
{
myEasterEgg = @"";
} else {
myEasterEgg = [myEasterEgg stringByAppendingString:@"2"];
}
}

-(IBAction)button3:(id)sender
{
if(CFStringCompare((CFStringRef)myEasterEgg, (CFStringRef)@"52235", 1) == 0)
{
myEasterEgg = @"";
} else {
myEasterEgg = [myEasterEgg stringByAppendingString:@"3"];
}
}

-(IBAction)button4:(id)sender
{
if(CFStringCompare((CFStringRef)myEasterEgg, (CFStringRef)@"52235", 1) == 0)
{
myEasterEgg = @"";
} else {
myEasterEgg = [myEasterEgg stringByAppendingString:@"4"];
}
}

-(IBAction)button5:(id)sender
{
if(CFStringCompare((CFStringRef)myEasterEgg, (CFStringRef)@"52235", 1) == 0)
{
myEasterEgg = @"";
} else {
myEasterEgg = [myEasterEgg stringByAppendingString:@"5"];
}
}

-(void)viewDidLoad
{
myEasterEgg = [[NSString alloc] initWithString:@""];
}

Answer 1

您正在泄漏原始字符串，并用新值替换它而不保留它们。崩溃的发生是因为你在一个悬空指针上调用[myEasterEgg stringByAppendingString:…]，也就是说，一个不再引用任何对象的变量。请参阅Memory Management Programming Guide 了解更多信息。