property测试代码：

//
//  main.m
//  TestVar2
//
//  Created by lishujun on 14-9-4.
//  Copyright (c) 2014年 lishujun. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Address : NSObject<NSCopying>
-(void) toString;
@end

@implementation Address
-(void) toString
{
    NSLog(@"this is an address");
}

-(id) copyWithZone:(NSZone *)zone
{
    Address *newAddress = [[Address alloc]init];
    return newAddress;
}
@end

@interface Employee : NSObject
@property (copy) Address *address; // assign, retain, copy
@end

@implementation Employee
@synthesize address;
@end

void testAssignAndRetain()
{
    // 创建他们应该都是1
    Address *address = [[Address alloc]init];
    Address *address2 = [[Address alloc]init];

    NSLog(@"a1 = %lu", [address retainCount]);
    NSLog(@"a2 = %lu", [address2 retainCount]);

    // 首次赋值看看会不会retain
    Employee *employee = [[Employee alloc]init];
    [employee setAddress: address];
    NSLog(@"a1 = %lu", [address retainCount]);
    NSLog(@"a2 = %lu", [address2 retainCount]);

    // 看看employee.address 和 address还是不是同一个对象
    [employee setAddress:address];
    NSLog(@"obj address          is %@" , address);
    NSLog(@"obj employee.address is %@" , employee.address);

    // 再次赋值看看会不会release
    [employee setAddress:address2];
    NSLog(@"a1 = %lu", [address retainCount]);
    NSLog(@"a2 = %lu", [address2 retainCount]);

    // 看看使用的时候会不会retain
    for (int i=0; i<10; i++) {
        [employee.address toString];
        NSLog(@"a2 = %lu", [address2 retainCount]);
    }
}

void testCopy1()
{
    Address *address = [[Address alloc]init];
    Address *address2 = [[Address alloc]init];
    Employee *employee = [[Employee alloc]init];

    // 看看employee.address 和 address还是不是同一个对象
    [employee setAddress:address];
    NSLog(@"%@" , address);
    NSLog(@"%@" , address2);
    NSLog(@"%@" , employee.address);

    // 看看employee.address 和 address还是不是同一个对象
    [employee setAddress:address2];
    NSLog(@"%@" , address);
    NSLog(@"%@" , address2);
    NSLog(@"%@" , employee.address); //之前的对象被替换
}

void testCopy2()
{
    Address *address = [[Address alloc]init];
    Employee *employee = [[Employee alloc]init];
    [employee setAddress:address];

    // 看看使用对象会不会retain
    for (int i=0; i<10; i++) {
        //[employee.address toString];
        NSLog(@"address = %lu", [address retainCount]);
        NSLog(@"e.address = %lu", [employee.address retainCount]);
    }

}

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        //testAssignAndRetain();
        testCopy2();
    }
    return 0;
}