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];}