iphone - 从 char * 获取 NSString(转换 C 的字符指针)

Question

我想在 UITextField 中显示 char *

我尝试过的:

char *data;
char *name=data+6;
txtName.text=[[NSString alloc] initWithCString:name encoding:NSUTF8StringEncoding];

但我没有得到正确的值。

Answer 1

要从 const char * 创建一个 NSString，只需使用这些方法:

返回一个 autoreleased 对象:

/**
 * Should be wrapped in `@autoreleasepool {...}`,
 * somewhere not far in call-stack
 * (as closer it's, the lower our memory usage).
 */
NSString *stringFromChar(const char *input) {
    return [NSString stringWithUTF8String: input];
}

Whenever we return an object (maybe to Swift), we need to register into nearest @autoreleasepool block (by calling autorelease method to prevent memory-leak, according to ownership-rules), but ARC does that automatically for us.

但即使禁用了 ARC，我们也不会被迫手动调用 autorelease，例如:

return [[NSString stringWithUTF8String: name] autorelease];

Generally, convenience factory methods (like stringWithUTF8String:), already call the autorelease method (or should if ARC disabled), because the class simply does not intend to own the instance.

创建一个保留对象:

NSString *result = [[NSString alloc] initWithUTF8String: name];

// ... Do something with resulted object.

// NOTE: calling below is not required
// (If ARC enabled, and should cause compile error).
[result release];

Update 2021 about difference; With ARC enabled, these two methods are equivalent (i.e. ARC will auto-call autorelease method; always registering to nearest @autoreleasepool).

Reference .

如果您没有获得正确的值，则说明数据有问题。添加一些 NSLog 调用以查看字符串包含的内容。