Question

#import <Foundation/Foundation.h>

@interface Engine : NSObject {
    NSMutableString *mutableName;
}

@property (assign)  NSMutableString *mutableName;

@end

Why does my ivar, engine.name not work with this simple NSMutableString method? mutableName is an NSMutableString and has been correctly implemented with @property and @synthesize.

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

int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    Engine *engine = [[Engine alloc]init];


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

int main (int argc, const char * argv[])
{

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Engine *engine = [[Engine alloc]init];

engine.mutableName = @"Jones";
[engine.mutableName insertString:@"Mrs." atIndex:0];
NSLog(@"Full name is %@", engine.mutableName);

}

    [pool drain];
    return 0;
}

#import "Engine.h"

@implementation Engine

@synthesize mutableName;

@end

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

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

    engine.mutableName = @"Jones";
    [engine.mutableName insertString:@"Mrs." atIndex:0];
    NSLog(@"Full name is %@", name);

    [pool drain];
    return 0;
}

Answer 1

你没有显示你的代码,但我怀疑你所做的事情是:<条码><>>>和<条码>可更改的Name ,并且为了在世系使用相同的ivar。在此情况下,您的<代码>可变性Name 财产,在被宣布为NSMutableString时,实际上将分配给<代码><> 姓名>/代码>的财产退回。如果是你重新做的,而且你真的想这样做,那么你需要修改你的<条码>。浏览器如以下(假设_name):背书:

- (NSString *)name {
    return [[_name copy] autorelease]; // take a snapshot of the string
}
- (void)setName:(NSString *)name {
    [_name release];
    _name = [_name mutableCopy];
}

这样一来,护str就被保留在hood子下,但在使用<条码>名称/代码>时,作为不可改变的扼杀。

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