NSString 问题

发布于 2024-12-17 03:18:04 字数 1211 浏览 5 评论 0原文

我在 Mac OS X 上使用简单的 NSString 时遇到问题：

NSString *letters = @"abcdefghijklmnopqrstuvwxyz0123456789";
myString = [myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]];

当我尝试再次访问该字符串时，Xcode 返回 EXC_BAD_ACCESS 当我使用格式 @"%c" 时，就会发生此错误当我使用 @"%@" 时，有时会出现相同的错误，有时会出现此字符串：control 0x10040a480，有时会出现以下情况：

{(
    <CFRunLoopObserver 0x10015ac60 [0x7fff70731ee0]>{locked = No, valid = Yes, activities = 0x21, repeats = Yes, order = 0, callout = _ZL15FlushAllBuffersP19__CFRunLoopObservermPv (0x7fff88a147d4), context = <CFRunLoopObserver context 0x0>}
)}

即使我不更改代码中的任何内容，错误也会随机发生，并且重新运行它。

我尝试通过以下方式获取随机字符串：

randomString = @"";
    NSString *letters = @"abcdefghijklmnopqrstuvwxyz0123456789";
    srand(time(NULL));
    for (int i=0; i<5; i++)
    {
        randomString = [randomString stringByAppendingFormat:@"%c", [letters characterAtIndex:(rand()%[letters length])]];
    }

randomString 在 header.h 中声明我也尝试过使用 NSMutableString 但这也不起作用。每次我尝试通过 @"%@" 访问字符串（或可变字符串）时，我都会收到 EXC_BAD_ACCESS

有什么想法吗？希望有人能帮助我！

问候，朱利安

原文

I have problems with a simple NSString on Mac OS X:

NSString *letters = @"abcdefghijklmnopqrstuvwxyz0123456789";
myString = [myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]];

When I try to access this string again, Xcode is returning EXC_BAD_ACCESS
This error just occures, when I'm using the format @"%c"
When I'm using @"%@", sometimes the same error, sometimes this string: control 0x10040a480 and sometimes this:

{(
    <CFRunLoopObserver 0x10015ac60 [0x7fff70731ee0]>{locked = No, valid = Yes, activities = 0x21, repeats = Yes, order = 0, callout = _ZL15FlushAllBuffersP19__CFRunLoopObservermPv (0x7fff88a147d4), context = <CFRunLoopObserver context 0x0>}
)}

The errors occur randomly even, if I don't change anything in the code and re-run it.

I try to get a random String by doing:

randomString = @"";
    NSString *letters = @"abcdefghijklmnopqrstuvwxyz0123456789";
    srand(time(NULL));
    for (int i=0; i<5; i++)
    {
        randomString = [randomString stringByAppendingFormat:@"%c", [letters characterAtIndex:(rand()%[letters length])]];
    }

randomString is declared in header.h
I also tried using a NSMutableString but that didn't work too.
Every time I try to access the string (or mutable string) via @"%@" I'm getting EXC_BAD_ACCESS

Any idea?
Hope somebody can help me!

Greets,
Julian

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甲如呢乙后呢 2024-12-24 03:18:04

您的问题是 myString 在您访问它之前会自动释放。

您需要将：更改

myString = [myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]];

为：

myString = [[myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]] retain];

完成后记得运行 [myString release]; 。

Your problem is that myString gets autoreleased before you access it.

You need to change:

myString = [myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]];

to:

myString = [[myString stringByAppendingFormat:@"%c", [letters characterAtIndex:3]] retain];

Remember to run [myString release]; when you are done with it.

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世界等同你 2024-12-24 03:18:04

这对我有用：

在文件顶部定义字母：

#define letters @"abcdefghijklmnopqrstuvwxyz0123456789"

然后附加一个随机字符，如下所示：

NSString *randomString = @"";

for (int i = 0; i < 5; i++) 
{
    UInt64 index = rand() % [letters length];
    NSString *randomCharacter = [letters substringWithRange: NSMakeRange(index, 1)];
    randomString = [randomString stringByAppendingString:randomCharacter];
}

NSLog(@"%@", randomString);

this works for me:

define letters at top of file:

#define letters @"abcdefghijklmnopqrstuvwxyz0123456789"

then append a random character like this:

NSString *randomString = @"";

for (int i = 0; i < 5; i++) 
{
    UInt64 index = rand() % [letters length];
    NSString *randomCharacter = [letters substringWithRange: NSMakeRange(index, 1)];
    randomString = [randomString stringByAppendingString:randomCharacter];
}

NSLog(@"%@", randomString);

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