Question

I’d appreciate some feedback on a particular approach I’m thinking of using. The scenario is below.

I have an object (lets call it MObject) that has a number of properties, say, x and y coordinates, height and width. The properties are named according to the KVC guidelines (MObject.x; MObject.height, etc). My next task, is to read in an XML file that describes this MObject. Unfortunately, the XML elements are named differently — X and Y, Height and Width (note the capitalization).

Ideally, the XML elements would match up with MObject’s properties. In this case, I could use KVC and avoid a whole whack of code:

for (xmlProperty in xmlElement) {     [MObject setValue:xmlProperty.value forKey:xmlProperty.name]. } 

One way of approaching this would be to make use of case-insensitive keys. Where would I start with that? Are there any other, better solutions?

Suggestions very much appreciated.

Answer 1

Don’t override -[NSObject valueForKey:] and -[NSObject setValue:forKey:] if you can at all help it.

Your best bet would be to convert the keys you get from the XML file on the fly. Use a separate method to do the conversion and you can also maintain a cache of names to property keys, so you only need to do each conversion once.

- (NSString *)keyForName:(NSString *)name {     // _nameToKeyCache is an NSMutableDictionary that caches the key     // generated for a given name so it's only generated once per name     NSString *key = [_nameToKeyCache objectForKey:name];     if (key == nil) {         // ...generate key...         [_nameToKeyCache setObject:key forKey:name];     }     return key; }  - (void)foo:xmlElement {     for (xmlProperty in xmlElement) {         [myObject setValue:xmlProperty.value forKey:[self keyForName:xmlProperty.name]].     } }