objective-c how to create an enumeration array with its string values as keys?

Question

i have an enumeration say gender, now i want to associate it to string values to use in the view inside a picker view. It's cocoa-touch framework and objective-c as language. So i don't know of a way to set the data source of the picker view as the enumeration, as could have been done in other frameworks. So i've been told i have to make array of enum values. and then i tried to add thos into an NSMutableDictionary with their respective string values. So i ended up with

NSArray* genderKeys = [NSArray arrayWithObjects:@"Male",@"Female",nil] ;
NSArray* genderValues = [NSArray arrayWithObjects:[NSNumber numberWithInt:male],[NSNumber numberWithInt:female],nil];

for(int i =0;i<[genderKeys count];i++)
    [_genderDictionary setValue:[genderValues objectAtIndex:i] forKey:[genderKeys objectAtIndex:i]];

and it's not working saying it's not a valid key, and i've read the key-coding article and i know now what's key and whats keypath, but still how can i solve that. It's ruining my life, Please help.

Sorry guys, i was using NSDictionary for _genderDictionary.But i had in my mind that it was nsmutable. Thank you all.

Alex Brown · Accepted Answer · 2010-11-25 12:38:44Z

2

Be careful using UI text as keys into your database. What amount when you need to localise your application to french, chinese, arabic etc?

answered Nov 25, 2010 at 12:38

Alex Brown

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Kenny Winker Over a year ago

dictionary keys shouldn't really ever be something that is exposed to the user. Not because of the language issue so much as because it's bass-ackwards. The key is what you use to retrieve the data, not the data itself.

Kenny Winker · Accepted Answer · 2010-11-25 12:39:31Z

That works for me. Running this (your code, with the first line added so it would compile) seems to work fine.

NSMutableDictionary *_genderDictionary = [NSMutableDictionary dictionary];
NSArray* genderKeys = [NSArray arrayWithObjects:@"Male",@"Female",nil] ;
NSArray* genderValues = [NSArray arrayWithObjects:[NSNumber numberWithInt:1],[NSNumber numberWithInt:2],nil];

for(int i =0;i<[genderKeys count];i++)
    [_genderDictionary setValue:[genderValues objectAtIndex:i] forKey:[genderKeys objectAtIndex:i]];

NSLog()-ing _genderDictionary outputs this

{
    Female = 2;
    Male = 1;
}

edit: re-reading your question, makes me think what you are looking for is the delegate methods of UIPickerView... implementing –pickerView:titleForRow:forComponent: is where you set the text that appears in the picker. If you have an NSArray of genders, you would do something like return [_genderArray objectAtIndex:row]; That way you don't need to fuss around with a dictionary and keys.

edit 2: a picker's datasource can't be an NSArray or NSDictionary directly. It has to be an object that implements UIPickerView's datasource/delegate protocol (which I suppose you could do with a subclass of NSArray, but that'd be cah-ray-zay!).

Thomas Zoechling · Accepted Answer · 2010-11-25 12:23:53Z

0

If I understand you correctly, you try to create a pre-populated dictionary.
You could use [NSDictionary dictionaryWithObjectsAndKeys:] for that.

[NSDictionary dictionaryWithObjectsAndKeys:
    [NSNumber numberWithUnsignedInt:0], @"Male", 
    [NSNumberWithUnsignedInt:1], @"Female", nil]

answered Nov 25, 2010 at 12:23

Thomas Zoechling

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