KVO实现自定义文件复制进度效果

NSString * path=NSHomeDirectory();
  path =[path stringByAppendingPathComponent:@"deskTop/Boby.m"];
  
  NSString * target=NSHomeDirectory();
  target =[target stringByAppendingPathComponent:@"deskTop/target.m"];
  
  NSFileManager * manager=[NSFileManager defaultManager];
  
  
  //校验并且创建文件
  if(![manager fileExistsAtPath:path]){
    [manager createFileAtPath:path contents:nil attributes:nil];
  }
  
  if(![manager fileExistsAtPath:target]){
    [manager createFileAtPath:target contents:nil attributes:nil];
  }
  NSDictionary * dic=[manager attributesOfItemAtPath:path error:nil];
  
  NSFileHandle * handle=[NSFileHandle fileHandleForReadingAtPath:path];
  NSFileHandle * handletTarget=[NSFileHandle fileHandleForWritingAtPath:target];
  
  int total=(int)[dic[@"NSFileSize"] integerValue];
  self.totalSize=total;
  int per=50;
  int count=total%per==0?total/per:total/per+1;
  for(int i=0;i<count;i++){
    
    [handle seekToFileOffset:self.nowSize];
    NSData *data= [handle readDataOfLength:per];
    
    int tem=per*(i+1);
    if(tem>total){
      tem=total;
    }

    self.nowSize=tem;
 
    [handletTarget seekToEndOfFile];
    [handletTarget writeData:data];
    [NSThread sleepForTimeInterval:0.2];
    
  }
  
  [handle closeFile];
[handletTarget closeFile];

- (id) initWithFile:(FileMake *)files{
  self=[super init];
  
  if(self){
    self.file= files;
    [self.file addObserver:self forKeyPath:@"nowSize" options:NSKeyValueObservingOptionNew context:nil];
  }
  return self;
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  CGFloat all=self.file.totalSize;
  CGFloat now=[[change objectForKey:@"new"] floatValue];
  CGFloat result=now/all; 
  NSLog(@"%.2f",result);
  //一定不能忘了销毁当前的观察者
  if(result==1){
    [self.file removeObserver:self forKeyPath:@"nowSize"];
  }
}

- (void) begin{
  [self.file startCopy];
}