深拷贝就是生成一个新的对象，内容和原对象完全相同。浅拷贝即是指针的拷贝，生成一个新的指针指向原对象
#import <Foundation/Foundation.h>
#import "Student.h"
#import "GoodStudent.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
/*
拷贝的意义：
在改变副本对象的时候，不会影响到原对象
定义：
深拷贝：就是拷贝出来一个新的对象，内容和原对象一样。
浅拷贝：其实就是指针的拷贝，没有一个新的对象生成，只是多了一个指向原对象的指针，将原对象的指针赋值给了新声明的指针，即，是一个指针的拷贝。
*/
// 只有从不可变对象copy到不可变对象的时候才是浅拷贝，其他的都是深拷贝
NSString *string = @"abcde";
NSString *str = [string copy];
NSLog(@"string: %@", string);
NSLog(@"str: %@", str);
// 因为指向同一个对象，所以原对象的引用计数+1
NSLog(@"string和str是否是同一个对象: %d", string == str);
// 由可变字符到不可变字符的copy是深拷贝
NSMutableString *mutableString = [NSMutableString stringWithFormat:@"abc%@", @"dddddd"];
NSString *str1 = [mutableString copy];
NSLog(@"mutableString和str1是否是同一个对象: %d", mutableString == str1);
// mutalbeCopy都是深拷贝
NSString *str2 = @"abbbbbbb";
NSMutableString *mutableString1 = [str2 mutableCopy];
NSLog(@"str2和mutableString1是否是同一个对象: %d", str2 == mutableString1);
// 由此可见，即使是不可变到不可变的mutableCopy也是深拷贝，进一步证明了mutableCopy是深拷贝
NSString *str3 = @"kkkkkkk";
NSString *string1 = [str3 mutableCopy];
NSLog(@"str3和string1是否是同一个对象: %d", str3 == string1);
NSMutableString *myStr1 = [NSMutableString stringWithFormat:@"abc%d", 10];
NSMutableString *myStr2 = [myStr1 copy];
// 这里的myStr2实际是一个immutable对象，是不可变的，所以改变myStr2对象会报错
// [myStr2 appendString:@"fdsaf"];
NSLog(@"myStr1: %@", myStr1);
NSLog(@"myStr2: %@", myStr2);
NSLog(@"myStr1和myStr2是否是同一个对象: %d", myStr1 == myStr2);
// 如果有改变副本的内容而保持原来的对象内容不变的话，那么就用copy属性
// 这里改变了mutableName但是stu的name属性值没变
Student *stu = [[Student alloc] init];
NSMutableString *mutableName = [NSMutableString stringWithFormat:@"aaaaaa%d", 10];
stu.name = mutableName;
[mutableName appendString:@" fdsafdsafsad"];
NSLog(@"stu.name: %@", stu.name);
NSLog(@"mutableName: %@", mutableName);
NSLog(@"stu.name和mutableName是否是同一个对象: %d", stu.name == mutableName);
Student *stu1 = [Student studentWithName:@"stu1"];
Student *stu2 = [stu1 copy];
NSLog(@"%@", stu1.name);
NSLog(@"%@", stu2.name);
stu2.name = @"stu2";
NSLog(@"%@", stu1.name);
NSLog(@"%@", stu2.name);
GoodStudent *goodStudent1 = [GoodStudent goodStudentWithAge:10 name:@"Jack"];
GoodStudent *goodStudent2 = [goodStudent1 copy];
goodStudent2.name = @"Tom";
goodStudent2.age = 20;
NSLog(@"goodStudent1 -> name: %@, age: %ld", goodStudent1.name, goodStudent1.age);
NSLog(@"goodStudent2 -> name: %@, age: %ld", goodStudent2.name, goodStudent2.age);
}
return 0;
}
#import <Foundation/Foundation.h>
@interface Student : NSObject <NSCopying>
@property (nonatomic, copy) NSString *name;
+ (id)studentWithName:(NSString *)name;
@end
#import "Student.h"
@implementation Student
+ (id)studentWithName:(NSString *)name {
// 这里右边需要写成self class这样，因为如果子类调用父类的这个方法的时候，就会产生相应的子类，而不是产生父类
// 左边不用动，这表现了面向对象的特点，多态
Student *stu = [[[self class] alloc] init];
stu.name = name;
return stu;
}
- (id)copyWithZone:(NSZone *)zone {
Student *copy = [[[self class] allocWithZone:zone] init];
copy.name = self.name;
return copy;
}
@end
#import <Foundation/Foundation.h>
#import "Student.h"
@interface GoodStudent : Student
@property (nonatomic, assign) NSInteger age;
+ (id)goodStudentWithAge:(int)age name:(NSString *)name;
@end
#import "GoodStudent.h"
@implementation GoodStudent
+ (id)goodStudentWithAge:(int)age name:(NSString *)name {
GoodStudent *good = [GoodStudent studentWithName:name];
good.age = age;
return good;
}
- (id)copyWithZone:(NSZone *)zone {
// 一定要调用父类的方法
GoodStudent *copy = [super copyWithZone:zone];
copy.age = self.age;
return copy;
}
@end
