OC中属性的内存管理

在MRC模式下,我们建一个Person类的对象.h文件如下

#import <Foundation/Foundation.h>

@interface Person : NSObject
@property (nonatomic, retain)NSString *name;
@property (nonatomic, retain)NSString *sex;
@property (nonatomic, assign)NSInteger age;
//自定义初始化
-(instancetype)initWithName:(NSString *)name Sex:(NSString *)sex Age:(NSInteger)age;
//便利构造器

+(instancetype)personWithName:(NSString *)name Sex:(NSString *)sex Age:(NSInteger)age;

@end

.m文件如下

#import "Person.h"

@implementation Person
//在MRC下,如果需要同时重写setter和getter方法,必须下面的的语句
@synthesize name = _name;
//自定义初始化
-(instancetype)initWithName:(NSString *)name Sex:(NSString *)sex Age:(NSInteger)age
{
    if (self = [super init]) {
        _name = name;
        _sex = sex;
        _age = age;
    }
    return self;
}
//便利构造器

+(instancetype)personWithName:(NSString *)name Sex:(NSString *)sex Age:(NSInteger)age
{
    return [[[Person alloc] initWithName:name Sex:sex Age:age]autorelease];
}
//重写dealloc可以验证对象内存空间是否被收回,方式是否被调用
-(void)dealloc
{
    NSLog(@"这个对象被销毁");
    //以后只要在MRC中,重写dealloc方法,就需要一一对应为语义特征为retain或者copy的属性生成的实例变量release一次
    [self.name release];//针对sertter方法最后一次retain的release
    [_sex release];
    [super dealloc];
}
//MRC下,retain的内部实现 setter方法
//-(void)setName:(NSString *)name
//{
//    if (_name != name) {
//        [_name release];
//        _name = [name retain];
//    }
//}
//-(NSString *)name
//{
//    return [[_name retain]autorelease];
//}
-(void)setName:(NSString *)name
{
    if (_name != name) {
        [_name release];
        _name = [name copy];
 
    }
}
-(NSString *)name
{
    return [[_name retain]autorelease];
}
@end

在MRC模式下,copy与retain的setter,getter方法写法一致,但是实现的机制不相同,前者是得到传入参数的副本,重新开辟空间,而后者是使引用计数加一