如何将NSString转换为NSData？ 数据的内容与字符串相同

Question

NSString * theString=@"e88d";
NSData * data;

// something I should implement

NSLog(@"%@", theString);

NSLog(@"%@",[data description]);

I want the results of the two printings to be the same.

---

AES encryption and decryption:

(1).The server:

If the plaintext is @"abcd";

The AES encrypted data(NSData data type) is "d882830c dc892036 4345839f 13c7516a"

(2).in my local app, my code is:

NSData*data=[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://..."]]; 
NSString * mystring= [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

However, to decrypt data successfully, I must have a data(NSData date type) which equals to "d882830c dc892036 4345839f 13c7516a" . But it is the mystring(NSString data type) not the data(NSData data type) that equals the right value.

The encryption and decryption function both need a data(NSData data type) as input datas.

- (NSData*)AES128EncryptWithKey:(NSString*)key;
- (NSData*)AES128DecryptWithKey:(NSString*)key;

Answer 1

I think this might answer your question

How do I convert a NSString value to NSData?

Answer 2

the description you wanna set is not an instance specific value. It's the description of the class/object. NSData will have a description of like: 'this is a data object'. You can override this value thou by overriding the method.

- (NSString *)description {
    return @"e88d"; //normally used for class description
}

Ofcourse you will have to inherit the NSData object for that and then override the description like code above.

PS. I dont think you wanna use description for this just explaining what the use of it is in every class.

---

What you might want is:

NSString * theString=@"e88d";
NSData * data=[theString dataUsingEncoding:NSUTF8StringEncoding];

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

Answer 3

@interface NSString (Joke)
- (NSString *)description;
@end
@implementation NSString (Joke)
- (NSString *)description
{
    return @"Panda!";
}
@end

@interface NSData (Joke)
- (NSString *)description;
@end
@implementation NSData (Joke)
- (NSString *)description
{
    return @"Panda!";
}
@end

Answer 4

How about this

NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://..."]];
NSData *decryptedData = [data AES128DecryptWithKey:key];
NSString *mystring = [[NSString alloc] initWithData:decryptedData encoding:NSUTF8StringEncoding];