关于IOS内存管理和ARC模式下的引用计数

Question

问题1：引用计数是针对的对象，还是针对存放数据的内存？
若说是指向对象。但当用Strong修饰时。我把 t2 = t0;t0,t1,t3的引用计数都增加了1 变成了3，说明是针对内存的。
若说时针对内存。但当用weak修饰t1时,t0,t1,t2 都是指向同一个内存地址：0x1c401eef0 但从日志中可以看出他们的引用计数时不相同的。所以就有问题1

问题2：当我用weak修饰t1时，把t1 = t0。因为时weak修饰的t1 所以t0 的引用计数没有改变，仍然是1; 但是为什么t1的引用计数仍然+1 变成了2？ （见下方日志）

#import "ViewController.h"


@interface RCTest ()
@property(nonatomic,copy)NSMutableString *s;
@end
@implementation RCTest

@end

@interface ViewController ()
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    RCTest *t0 = [[RCTest alloc] init];
    RCTest *t1;
    RCTest *t2;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t1 = t0;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t2 = t0;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t1 = nil;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
}
@end

日志：

2018-11-25 23:15:50.096611+0800 TestApp[2144:124995] 
2018-11-25 23:15:50.096789+0800 TestApp[2144:124995] t0:0x1c4014b10,t1:0x0,t2:0x0
2018-11-25 23:15:50.096909+0800 TestApp[2144:124995] t0:1,t1:(null),t2:(null)
2018-11-25 23:15:50.096989+0800 TestApp[2144:124995] 
2018-11-25 23:15:50.097051+0800 TestApp[2144:124995] t0:0x1c4014b10,t1:0x1c4014b10,t2:0x0
2018-11-25 23:15:50.097141+0800 TestApp[2144:124995] t0:2,t1:2,t2:(null)
2018-11-25 23:15:50.097216+0800 TestApp[2144:124995] 
2018-11-25 23:15:50.097278+0800 TestApp[2144:124995] t0:0x1c4014b10,t1:0x1c4014b10,t2:0x1c4014b10
2018-11-25 23:15:50.098235+0800 TestApp[2144:124995] t0:3,t1:3,t2:3
2018-11-25 23:15:50.098356+0800 TestApp[2144:124995] 
2018-11-25 23:15:50.098425+0800 TestApp[2144:124995] t0:0x1c4014b10,t1:0x0,t2:0x1c4014b10
2018-11-25 23:15:50.098522+0800 TestApp[2144:124995] t0:2,t1:(null),t2:2

当用weak修饰时：

#import "ViewController.h"


@interface RCTest ()
@property(nonatomic,copy)NSMutableString *s;
@end
@implementation RCTest

@end

@interface ViewController ()
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    RCTest *t0 = [[RCTest alloc] init];
    __weak RCTest *t1;
    RCTest *t2;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t1 = t0;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t2 = t0;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
    t1 = nil;
    NSLog(@"\n");
    NSLog(@"t0:%p,t1:%p,t2:%p",t0,t1,t2);
    NSLog(@"t0:%@,t1:%@,t2:%@",[t0 valueForKey:@"retainCount"],[t1 valueForKey:@"retainCount"],[t2 valueForKey:@"retainCount"]);
}
@end

日志

2018-11-25 23:17:09.154880+0800 TestApp[2161:126259] 
2018-11-25 23:17:09.155053+0800 TestApp[2161:126259] t0:0x1c401eef0,t1:0x0,t2:0x0
2018-11-25 23:17:09.155442+0800 TestApp[2161:126259] t0:1,t1:(null),t2:(null)
2018-11-25 23:17:09.155544+0800 TestApp[2161:126259] 
2018-11-25 23:17:09.155610+0800 TestApp[2161:126259] t0:0x1c401eef0,t1:0x1c401eef0,t2:0x0
2018-11-25 23:17:09.155736+0800 TestApp[2161:126259] t0:1,t1:2,t2:(null)
2018-11-25 23:17:09.155811+0800 TestApp[2161:126259] 
2018-11-25 23:17:09.155875+0800 TestApp[2161:126259] t0:0x1c401eef0,t1:0x1c401eef0,t2:0x1c401eef0
2018-11-25 23:17:09.155969+0800 TestApp[2161:126259] t0:2,t1:3,t2:3
2018-11-25 23:17:09.156042+0800 TestApp[2161:126259] 
2018-11-25 23:17:09.156103+0800 TestApp[2161:126259] t0:0x1c401eef0,t1:0x0,t2:0x1c401eef0
2018-11-25 23:17:09.156195+0800 TestApp[2161:126259] t0:2,t1:(null),t2:2

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