局部对象变量调用分线程方法

demo1.

@implementation PEKViewController

-(void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor redColor];
 

    PEKNewThread *newThread = [[PEKNewThread alloc] init];
    [newThread startLog];
    
}

@end

@implementation PEKNewThread

-(void)startLog
{
   [self performSelectorInBackground:@selector(log) withObject:nil];
//    [self log];<pre name="code" class="objc">typedef  void (^timeRreachBlock)(int times);

@interface PEKNewThread : NSObject
{
    int times;
}

-(void)startLog;
@property(nonatomic,copy)timeRreachBlock reachBlock;
@end

@implementation PEKNewThread

-(void)startLog
{
   [self performSelectorInBackground:@selector(log) withObject:nil];
//[self log];
}

-(void)log
{
    NSLog(@"I am log method");
    times ++;
    if (times == 3)
    {
        if (self.reachBlock)
        {
            [self reachBlock];
        }
    }
    [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(printLog) userInfo:nil repeats:YES];
}

-(void)printLog
{
    NSLog(@"log");
}

-(void)dealloc
{
    NSLog(@"I am newThead delloc");
}

@end

}-(void)log{ NSLog(@"I am log method"); [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(printLog) userInfo:nil repeats:YES];}-(void)printLog{ NSLog(@"log");}-(void)dealloc{ NSLog(@"I am newThead delloc");}@end

上述代码打印：


2014-08-07 14:24:44.453 ARCMemoryTest[17159:3507] I am log method
2014-08-07 14:24:44.454 ARCMemoryTest[17159:3507] I am newThead delloc
由上述demo可知，局部对象，调用分线程方法，方法一遍，对象就释放了。

demo2.
再来看一下，如果局部变量调用主线程的情况：

-(void)startLog
{
//   [self performSelectorInBackground:@selector(log) withObject:nil];
    [self log];
}

替换上述方法，打印结果如下：

2014-08-07 14:57:54.913 ARCMemoryTest[17240:60b] I am log method
2014-08-07 14:57:55.014 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.113 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.214 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.314 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.414 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.514 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.614 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.714 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.814 ARCMemoryTest[17240:60b] log
2014-08-07 14:57:55.914 ARCMemoryTest[17240:60b] log
demo3.
再来看一下如果局部变量分线程中有block块的情况：
设想：如果有对指向self的指针，调用方法的话，应该会crash，或者不调用该方法
验证：

@implementation PEKViewController

-(void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor redColor];
 

    PEKNewThread *newThread = [[PEKNewThread alloc] init];
    [newThread startLog];
     newThread.reachBlock = ^(int times)
    {
        NSLog(@"I am block I am excute");
    };
    
}

@end

typedef  void (^timeRreachBlock)(int times);

@interface PEKNewThread : NSObject
{
    int times;
}

-(void)startLog;
@property(nonatomic,copy)timeRreachBlock reachBlock;
@end

#import "PEKNewThread.h"

@implementation PEKNewThread

-(void)startLog
{
   [self performSelectorInBackground:@selector(log) withObject:nil];
//[self log];
}

-(void)log
{
    NSLog(@"I am log method");
    times ++;
    if (times == 3)
    {
        if (self.reachBlock)
        {
            [self reachBlock];
        }
    }
    [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(printLog) userInfo:nil repeats:YES];
}

-(void)printLog
{
    NSLog(@"log");
}

-(void)dealloc
{
    NSLog(@"I am newThead delloc");
}

@end

打印结果：

2014-08-07 15:12:54.943 ARCMemoryTest[17301:3507] I am log method
2014-08-07 15:12:54.944 ARCMemoryTest[17301:3507] I am newThead delloc
block没有打印，说明，block，如果局部对象调用异步方法的话，是需要被写成成员变量的（无论其中含有什么）
补充点常识：空指针调用方法不会奔溃，但是如果指针不为空，指向的内存释放了的话，就会奔溃，这也是为什么好多人都会习惯 self.property = nil，的原因