iphone - IOS初期化が_variableで失敗するのに、NSNumberのself.variableでは失敗しないのはなぜですか？

Question

私は次のクラスを持っています：

----.hファイル

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

@interface ServiceRequest : NSObject {
}

@property (strong, nonatomic) NSString *url;
@property (strong, nonatomic) NSString *postData;
@property (strong, nonatomic) NSNumber *requestId;
@property (strong, nonatomic) id<ServiceMapperDelegate> mapper;

-(id)initWithUrl:(NSString *)url andWithPostdata:(NSString *)postData;

@end

-------.mファイル

#import "ServiceRequest.h"

@implementation ServiceRequest

@synthesize url = _url, postData = _postData, requestId = _requestId, mapper = _mapper;

-(id)initWithUrl:(NSString *)url andWithPostdata:(NSString *)postData {
    if (self = [super init]) {
        _url = url;
        _postData = postData;
        self.requestId = [NSNumber numberWithInt:-1]; // HERE IS THE PROBLEM
    }
    return self;
}

@end

self.requestId = [NSNumber numberWithInt：-1];がなぜですか 。 動作しますが、 _requestId = [NSNumber numberWithInt：-1]; ランタイムエラーをスローしますか？

Answer 1

The class method [NSNumber numberWithInt:-1] is returning an autoreleased value. When you use the synthesized setter method, the value gets retained by the setter. When you bypass the setter, there is no retain... So as soon as the autorelease pool is drained you have a dangling pointer.