lldb error: use of undeclared identifier

问题

Anyone know whats going on here:

@implementation Test
{
    NSData *_data;
}

- (id)initWithData:(NSData *)data
{
    self = [super init];
    if (self)
    {
        _data = data;
    } 
    return self;  // BREAKPOINT HERE
}

From lldb:

(lldb) p data
(NSData *) $1 = 0x07f911e0 30308 bytes
(lldb) p _data
error: use of undeclared identifier '_data'
error: 1 errors parsing expression

Why can't I view _data?

回答1:

I've only ever seen data fields declared in an @interface block; you appear to be defining fields in the @implementation.

Try putting this in the header instead, e.g.

@interface Test
{
    NSData *_data;
}
. . .
@end

来源：https://stackoverflow.com/questions/11488361/lldb-error-use-of-undeclared-identifier