NSData类

概念:

如何将NSString转化成NSData(将字符串转化成二进制数据)

NSString *str = @"ABCDE";
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"%d",data.length);

如何将NSData转化成NSString;

 NSString *converted = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"%@",converted);

如何将图片数据转化成NSData(模拟在网上下载一张图片)

NSString *imagePath = [[NSBundle mainBundle]pathForResource:@"Lion" ofType:@"jpg"];
    
    NSData *imagedata = [NSData dataWithContentsOfFile:imagePath];
    
    UIImage * image = [UIImage imageWithData:imagedata];
    
    UIImageView *imageview = [[UIImageView alloc]initWithFrame:CGRectMake(100,300, 100, 100)];
    
    imageview.image = image;
    [self.view addSubview:imageview];