IOS学习笔记十八(copy、mutableCopy、NSCopying、NSMutableCopy、深复制、浅复制)

1、 copy、mutableCopy方法

copy方法返回对象的不可修改的副本

mutableCopy方法返回的对象可修改的副本

1)、测试demo

int main(int argc, char * argv[]) {
    @autoreleasepool {
        NSMutableString *book = [NSMutableString stringWithString:@"chenyu"];
        NSMutableString *bookCopy = [book mutableCopy];
        [bookCopy replaceCharactersInRange:NSMakeRange(1, 2) withString:@"gong"];
        NSLog(@"book is %@", book);
        NSLog(@"bookCopy is %@", bookCopy);
        
        NSString *str = @"chenyu";
        NSMutableString *strCopy = [str mutableCopy];
        [strCopy appendString:@"chenyu"];
        NSLog(@"strCopy is:%@", strCopy);
        //由于str2是不可变的，所以运行下面会报错
        NSMutableString *str2 = [str copy];
        NSLog(@"str copy chen is:%@", str2);
//        [str2 appendString:@"chenyu"];
    }
}

2)、运行结果

2018-07-15 19:03:35.564049+0800 cyTest[27254:9418105] book is chenyu
2018-07-15 19:03:35.565157+0800 cyTest[27254:9418105] bookCopy is cgongnyu
2018-07-15 19:03:35.566056+0800 cyTest[27254:9418105] strCopy is:chenyuchenyu
2018-07-15 19:03:35.566857+0800 cyTest[27254:9418105] str copy chen is:chenyu

2、NSCopying、NSMutableCopy协议

对象调用copy方法来复制自身的可变副本，需要类实现NSCopying协议，让该类实现copyWithZone方法

对象调用mutableCopy方法来复制自身的可变副本，需要类实现NSMutbaleCopying协议，让类实现mutableCopyWithZone方法demo可以看下下面写的浅复制

3、深复制和浅复制

我个人理解感觉浅复制是复制后的属性(指针变量)指向的地址都是同一块地址，当复制后的对象属性值发生变化的时候，原始值也发生了变化。

深复制就是复制后的属性(指针变量)指向的地址不是同一块地址，当复制后的对象属性值发生变化的时候，原始值不会发生变化。

1)、浅复制测试Demo

Dog.h

#import <Foundation/Foundation.h>
#ifndef Dog_h
#define Dog_h

@interface Dog : NSObject<NSCopying>
@property (nonatomic, strong) NSMutableString *name;
@property (nonatomic, assign) int age;
@end
#endif /* Dog_h */

Dog.m

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

@implementation Dog
@synthesize name;
@synthesize age;
-(id)copyWithZone:(NSZone *)zone
{
    Dog *dog = [[[self class] allocWithZone:zone] init];
    dog.name = self.name;
    dog.age = self.age;
    return dog;
}
@end

main.m

        Dog *dog1 = [Dog new];
        dog1.name = [NSMutableString stringWithString:@"chen"];
        dog1.age = 1;
        NSLog(@"dog1.name is %@ and age is %d", dog1.name, dog1.age);
        
        //浅复制
        Dog *dog2 = [dog1 copy];
//        dog2.name = [NSMutableString stringWithString:@"li"];
        [dog2.name replaceCharactersInRange:NSMakeRange(1, 2) withString:@"hel"];
        dog2.age = 20;
        NSLog(@"dog2.name is %@ and age is %d", dog2.name, dog2.age);
        NSLog(@"dog1.name is %@ and age is %d", dog1.name, dog1.age);

2)、运行结果

2018-07-15 19:03:35.567556+0800 cyTest[27254:9418105] dog1.name is chen and age is 1
2018-07-15 19:03:35.567690+0800 cyTest[27254:9418105] dog2.name is cheln and age is 20
2018-07-15 19:03:35.567768+0800 cyTest[27254:9418105] dog1.name is cheln and age is 1

3)、深复制Demo

Dog.h文件一样

Dog.m文件有点变化

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

@implementation Dog
@synthesize name;
@synthesize age;
-(id)copyWithZone:(NSZone *)zone
{
    Dog *dog = [[[self class] allocWithZone:zone] init];
//    dog.name = self.name;
    dog.name =  [self.name mutableCopy];
    dog.age = self.age;
    return dog;
}
@end

main.m文件一样

        Dog *dog1 = [Dog new];
        dog1.name = [NSMutableString stringWithString:@"chen"];
        dog1.age = 1;
        NSLog(@"dog1.name is %@ and age is %d", dog1.name, dog1.age);
        
        //深复制
        Dog *dog2 = [dog1 copy];
//        dog2.name = [NSMutableString stringWithString:@"li"];
        [dog2.name replaceCharactersInRange:NSMakeRange(1, 2) withString:@"hel"];
        dog2.age = 20;
        NSLog(@"dog2.name is %@ and age is %d", dog2.name, dog2.age);
        NSLog(@"dog1.name is %@ and age is %d", dog1.name, dog1.age);

4)、运行结果

2018-07-15 19:13:08.751335+0800 cyTest[27529:9427019] dog1.name is chen and age is 1
2018-07-15 19:13:08.751686+0800 cyTest[27529:9427019] dog2.name is cheln and age is 20
2018-07-15 19:13:08.751885+0800 cyTest[27529:9427019] dog1.name is chen and age is 1

4、setter方法的复制选项

我们setter方法复制选项的时候，如果加了copy属性，比如setName方法

-(void)setName : (NSMutableStrinfg *)name
{

    self.name  = [name copy];

}

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

@implementation Dog
@synthesize name;
@synthesize age;
@end

所以当对象设置了name属性的话，就不能再改变了，如下demo

Dog.h

#import <Foundation/Foundation.h>
#ifndef Dog_h
#define Dog_h

@interface Dog : NSObject
@property (nonatomic, copy) NSMutableString *name;
@property (nonatomic, assign) int age;
@end
#endif /* Dog_h */

Dog.m

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

@implementation Dog
@synthesize name;
@synthesize age;
@end

main.m

        Dog *dog1 = [Dog new];
        dog1.name = [NSMutableString stringWithString:@"chen"];
        dog1.age = 1;
        [dog1.name appendString:@"hello"];

运行结果

2018-07-15 19:22:17.736557+0800 cyTest[27853:9436238] -[NSTaggedPointerString appendString:]: unrecognized selector sent to instance 0xa0000006e6568634
2018-07-15 19:22:17.739655+0800 cyTest[27853:9436238] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSTaggedPointerString appendString:]: unrecognized selector sent to instance 0xa0000006e6568634'
*** First throw call stack:
(
	0   CoreFoundation                      0x0000000104fd61e6 __exceptionPreprocess + 294
	1   libobjc.A.dylib                     0x000000010466b031 objc_exception_throw + 48
	2   CoreFoundation                      0x0000000105057784 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
	3   CoreFoundation                      0x0000000104f58898 ___forwarding___ + 1432
	4   CoreFoundation                      0x0000000104f58278 _CF_forwarding_prep_0 + 120
	5   cyTest                              0x0000000103d60438 main + 600
	6   libdyld.dylib                       0x0000000108a2f955 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

很明显，报错了。