Encoding issue: An NSString into a key of an NSDictionary

问题

So I'm taking a data file and encoding it into a string:

                ///////////////////////////////
                // Get the string

                NSString* dataString = [[NSString alloc] initWithData:data
                                                             encoding:encoding];

                NSLog(@"dataString = %@",dataString);

The file was a list of French words and they NSLog fine, showing appropriate accents (just one example):

abandonnèrent

Now, in the very next part of the code I take this NSString of the file contents and convert it to a dictionary where the words are the keys and the objects are two additional dictionaries:

               ///////////////////////////////
               // Now parse the file (string)

                NSMutableDictionary *mutableWordlist = [[NSMutableDictionary alloc] init];

                int i = 0;
                for (NSString *line in [dataString componentsSeparatedByString:@"\n"]) {
                    NSArray *words = [line componentsSeparatedByString:@"\t"];

                    NSNumber *count = [NSNumber numberWithInt:(i+1)];

                    NSArray *keyArray;
                    NSArray *objectArray;


                    if ([words count] < 2) { // No native word
                        keyArray = [[NSArray alloc] initWithObjects:@"frequency",  nil];
                        objectArray = [[NSArray alloc] initWithObjects:count,  nil];

                    }
                    else {
                        keyArray = [[NSArray alloc] initWithObjects:@"frequency", @"native", nil];
                        objectArray = [[NSArray alloc] initWithObjects:count, [words[1] lowercaseString], nil];

                    }

                    NSDictionary *detailsDict = [[NSDictionary alloc] initWithObjects:objectArray forKeys:keyArray];

                    [mutableWordlist setObject:detailsDict forKey:[words[0] lowercaseString]];

                    i++;
                }


                self.wordlist = mutableWordlist;

                NSLog(@"self.wordlist = %@", self.wordlist);

But here the keys have encoding issues and log as so if they have an accent:

"abandonn\U00e8rent
" =     {
        frequency = 24220;
    };

What is happening?

回答1:

Nothing (wrong) is happening.

When you NSLog an NSString it is being output as Unicode text. However when you NSLog the NSDictionary they keys are being output with unicode escape sequences, \U00e8 is the escape code you can use in a string if you cannot type an è - say because your source file is in ASCII.

So the difference is only in how the string is being printed, the string is not different.

HTH

来源：https://stackoverflow.com/questions/21469627/encoding-issue-an-nsstring-into-a-key-of-an-nsdictionary