深.淺拷貝
- copy/mutableCopy NSString
NSString *string = @"漢斯哈哈哈";
// 沒(méi)有產(chǎn)生新對(duì)象
NSString *copyString = [string copy];
// 產(chǎn)生新對(duì)象
NSMutableString *mutableCopyString = [string mutableCopy];
NSLog(@"string = %p copyString = %p mutableCopyString = %p", string, copyString, mutableCopyString);
- copy/mutableCopy NSMutableString
NSMutableString *string = [NSMutableString stringWithString:@"漢斯哈哈哈"];
// 產(chǎn)生新對(duì)象
NSString *copyString = [string copy];
// 產(chǎn)生新對(duì)象
NSMutableString *mutableCopyString = [string mutableCopy];
NSLog(@"string = %p copyString = %p mutableCopyString = %p", string, copyString, mutableCopyString);
結(jié)論：
注意：其他對(duì)象NSArray铐望、NSMutableArray 、NSDictionary撑蒜、NSMutableDictionary一樣適用
- copy NSObject
HSPerson *p = [[HSPerson alloc] init];
p.age = 20;
p.height = 170.0;
HSPerson *copyP = [p copy]; // 這里崩潰
崩潰：
看崩潰信息HSPerson應(yīng)該先實(shí)現(xiàn)：
- (id)copyWithZone:(NSZone *)zone;
測(cè)試：
#import "HSPerson.h"
@interface HSPerson()<NSCopying>
@end
@implementation HSPerson
- (id)copyWithZone:(NSZone *)zone
{
return @"漢斯哈哈哈";
}
@end
HSPerson *p = [[HSPerson alloc] init];
p.age = 20;
p.height = 170.0;
HSPerson *copyP = [p copy];
NSLog(@"copyP: %@", copyP);
可以看出copyWithZone重新分配新的內(nèi)存空間逞姿，則：
- (id)copyWithZone:(NSZone *)zone
{
HSPerson *person = [[HSPerson allocWithZone:zone] init];
return person;
// 有些人可能下面alloc,重新初始化空間免钻，但這方法已給你分配了zone糯彬，自己就無(wú)需再次alloc內(nèi)存空間了
// HSPerson *person = [[HSPerson alloc] init];
}
HSPerson *p = [[HSPerson alloc] init];
p.age = 20;
p.height = 170.0;
HSPerson *copyP = [p copy];
NSLog(@"p = %p copyP = %p", p, copyP);
NSLog(@"age = %d height = %f", copyP.age, copyP.height);
雖然copy了份新的對(duì)象纽乱，然而age,height值并未copy薪前，那么：
- (id)copyWithZone:(NSZone *)zone
{
HSPerson *person = [[HSPerson allocWithZone:zone] init];
person.age = self.age;
person.height = self.height;
// 這里self其實(shí)就要被copy的那個(gè)對(duì)象润努，很顯然要自己賦值給新對(duì)象，所以這里可以控制copy的屬性
return person;
}
這時(shí)你會(huì)想示括，有NSMutableCopying？沒(méi)錯(cuò)痢畜，是有這貨：
- (id)mutableCopyWithZone:(NSZone *)zone
{
HSPerson *person = [[HSPerson allocWithZone:zone] init];
person.age = self.age;
person.height = self.height;
return person;
}
NSCopying垛膝、NSMutableCopying有啥區(qū)別？
其實(shí)感覺(jué)沒(méi)必要有NSMutableCopying丁稀，因?yàn)閴焊蜎](méi)可變的HSPerson吼拥，但如果該對(duì)象有其他行為，可以借用NSMutableCopying實(shí)現(xiàn)线衫，哈哈哈
property里的copy凿可、strong區(qū)別
說(shuō)完深淺拷貝，理解property里的copy授账、strong就輕松多了枯跑！
- copy
#import <Foundation/Foundation.h>
@interface HSPerson : NSObject
@property (nonatomic, copy) NSString *name;
@end
NSMutableString *string = [NSMutableString stringWithFormat:@"漢斯哈哈哈"];
HSPerson *person = [[HSPerson alloc] init];
person.name = string;
// 不能改變person.name的值，因?yàn)槠鋬?nèi)部copy新的對(duì)象
[string appendString:@" hans"];
NSLog(@"name = %@", person.name);
property copy 實(shí)際上就對(duì)name干了這個(gè)：
- (void)setName:(NSString *)name
{
_name = [name copy];
}
假設(shè)name為NSMutableString白热，會(huì)發(fā)生什么事敛助？
@property (nonatomic, copy) NSMutableString *name;
這樣會(huì)挨罵哦，實(shí)際上內(nèi)部還是：
- (void)setName:(NSMutableString *)name
{
_name = [name copy];
}
copy出來(lái)的仍然是不可變字符屋确！如果有人用NSMutableString的方法纳击，就會(huì)崩潰:
- strong
@property (nonatomic, strong) NSString *name;
NSMutableString *string = [NSMutableString stringWithFormat:@"漢斯哈哈哈"];
HSPerson *person = [[HSPerson alloc] init];
person.name = string;
// 可以改變person.name的值续扔，因?yàn)槠鋬?nèi)部沒(méi)有生成新的對(duì)象
[string appendString:@" hans"];
NSLog(@"name = %@", person.name);
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