Iphone 关于Objective-C中的复制属性
我测试了这个示例代码 样本hIphone 关于Objective-C中的复制属性,iphone,objective-c,ios,cocoa-touch,nsstring,Iphone,Objective C,Ios,Cocoa Touch,Nsstring,我测试了这个示例代码 样本h { NSString *string1; NSString *string2; NSMutableString *string3; } @property (assign) IBOutlet NSWindow *window; @property (strong,nonatomic) NSString *string1; @property (copy,nonatomic) NSString *string2; @property (s
{
NSString *string1;
NSString *string2;
NSMutableString *string3;
}
@property (assign) IBOutlet NSWindow *window;
@property (strong,nonatomic) NSString *string1;
@property (copy,nonatomic) NSString *string2;
@property (strong,nonatomic) NSMutableString *string3;
@end
#import "Sample.h"
@synthesize string1;
@synthesize string2;
@synthesize string3;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
string1 = [[NSString alloc] init];
string2 = [[NSString alloc] init];
string3 = [[NSMutableString alloc] initWithString:@"test"];
string2 = string3;
string1 = string3;
[string3 appendString:@"test"];
NSLog(@"%@",string1);
NSLog(@"%@",string2);
NSLog(@"%@",string3);
}
@end
2012-09-23 00:11:48.610 sample[13468:303] testtest
2012-09-23 00:11:48.611 sample[13468:303] testtest
2012-09-23 00:11:48.611 sample[13468:303] testtest
string2 is "test"
请告诉我，我睡不好。问题是，您没有访问属性，但是您正在立即操作备份实例变量。对于那些IVAR，
=string2 = string3;
string1 = string3
string3string1string2string3copystrongself.string2 = string3;
self.string1 = string3
string1 = [[NSString alloc] init];
string2 = [[NSString alloc] init];
但仍然如此。您不需要创建这些实例，也不需要直接
memcpy（）=string2 = string3;
string1 = string3
string3string1string2string3copystrongself.string2 = string3;
self.string1 = string3
string1 = [[NSString alloc] init];
string2 = [[NSString alloc] init];
但仍然如此。您不需要创建这些实例，也不需要直接
memcpy（）string2copystrongNSStringNSMutableString顺便说一句，这就是为什么应该在具有可变对等对象的对象上使用
copystring2copystrongNSStringNSMutableString顺便说一句，这就是为什么应该在具有可变对等对象的对象上使用
copy副本strongretaincopycopystrongretaincopy