oc数据类型的转换

1.NSString<->NSData

//NSString->NSData

NSString *s = [NSString new];

s = @"ssss";

NSData *d = [s dataUsingEncoding:NSUTF8StringEncoding];

NSLog(@"data:%s",d.bytes);//ssss

//NSData->NSString

NSString *str = [[NSString alloc] initWithData:d encoding:NSUTF8StringEncoding];

NSLog(@"str:%@",str);//ssss

2.NSString<->const char

//NSString-> const char

const char *c = [str UTF8String];

NSLog(@"c----%s",c);//ssss

//const char -> NSString

str = [[NSString alloc] initWithCString:c encoding:NSUTF8StringEncoding];

NSLog(@"%@",str);//ssss

3.NSData<->const char*

//NSData -> const char

const char *a = [data bytes];

NSLog(@"---%s",a);

//const char -> NSData

NSData *data1 = [[NSData alloc] initWithBytes:a length:10];

NSLog(@"%@",data1);

4.NSData<->Byte

//NSData->Byte

Byte *byte = (Byte *)[data1 bytes];

NSLog(@"byte----%s",byte);//ssss

//Byte->NSData

data1 = [[NSData alloc] initWithBytes:byte length:4];

NSLog(@"%@",data1);