IOS學習筆記十八(copy、mutableCopy、NSCopying、NSMutableCopy、深複制、淺複制)（1）

1、 copy、mutableCopy方法

copy方法傳回對象的不可修改的副本

mutableCopy方法傳回的對象可修改的副本

1)、測試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是不可變的，是以運作下面會報錯
        NSMutableString *str2 = [str copy];
        NSLog(@"str copy chen is:%@", str2);
//        [str2 appendString:@"chenyu"];
    }
}      

2)、運作結果

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協定

對象調用copy方法來複制自身的可變副本，需要類 實作NSCopying協定，讓該類實作copyWithZone方法

對象調用mutableCopy方法來複制自身的可變副本，需要類實作NSMutbaleCopying協定，讓類實作mutableCopyWithZone方法demo可以看下下面寫的淺複制

3、深複制和淺複制

我個人了解感覺淺複制是複制後的屬性(指針變量)指向的位址都是同一塊位址，當複制後的對象屬性值發生變化的時候，原始值也發生了變化。

深複制就是複制後的屬性(指針變量)指向的位址不是同一塊位址，當複制後的對象屬性值發生變化的時候，原始值不會發生變化。

1)、淺複制測試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);
        
        //淺複制
        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);      

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