NSString,NSData,NSURL,UIImage……互转

技巧：想要获得什么即以什么开头+With

1、NSString ——> NSURL       将字符串地址封装成可用的URL类型 

NSURL *url = [NSURL URLWithString:str];

2、NSURL ——> NSData

NSData *data = [NSData dataWithContentsOfURL:url];

3、NSData ——> UIImage

UIImage *image = [UIImage imageWithData:data];

4、UIImage ——> NSData

NSData *dataImagePng = UIImagePNGRepresentation(image);

NSData *dataImageJpg = UIImageJPEGRepresentation(image, 1);（第二个参数表示压缩的程度）

5、NSString ——> UIImage

UIImage *dataImageFile = [UIImage imageWithContentsOfFile:@""];

6、NSString ——> NSData

NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];

7、NSData ——> NSString

NSString *strdata = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];

8、NSURL ——> NSString

NSString * str = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];

9、NSData ——> NSDictionary

NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];