OC中 NSData转NSString，Byte，UIImage

1，NSData 与 NSString

　　NSData --> NSString

　　NSString *aString = [[NSString alloc] initWithData:adata encoding:NSUTF8StringEncoding];

　　NSString --> NSData

　　NSString *aString = @"1234";

　　NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

2，NSData 与 Byte

　　NSData --> Byte

　　NSString *testString = @"1234567890";

　　NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];

　　Byte *testByte = (Byte *)[testData bytes];

　　Byte --> NSData

　　Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};

　　NSData *adata = [[NSData alloc] initWithBytes:byte length:24];

3，NSData 与 UIImage

　　NSData --> UIImage

　　UIImage *aimage = [UIImage imageWithData: imageData];

　　//例：从本地文件沙盒中取图片并转换为NSData

　　NSString *path = [[NSBundle mainBundle] bundlePath];

　　NSString *name = [NSString stringWithFormat:@"ceshi.png"];

　　NSString *finalPath = [path stringByAppendingPathComponent:name];

　　NSData *imageData = [NSData dataWithContentsOfFile: finalPath];

　　UIImage *aimage = [UIImage imageWithData: imageData];

　　UIImage－> NSData

　　NSData *imageData = UIImagePNGRepresentation(aimae);

4，NSData 与 NSMutableData

　　NSData --> MSMutableData

　　NSData *data=[[NSData alloc]init];

　　NSMutableData *mdata=[[NSMutableData alloc]init];

　　mdata=[NSData dataWithData:data];