Question

I want to create instance variables dynamically at runtime, and I want to add these variables to a category. The number of the instance variables may change based on the configuration/properties file which I am using for defining them.

Any ideas??

Answer 1

I’d be inclined to just use a NSMutableDictionary (see NSMutableDictionary Class Reference). Thus, you would have an ivar:

NSMutableDictionary *dictionary;

You’d then initialize it:

dictionary = [NSMutableDictionary dictionary];

You can then save values to it dynamically in code, e.g.:

dictionary[@"name"] = @"Rob";
dictionary[@"age"] = @29;

// etc.

Or, if you are reading from a file and don’t know what the names of the keys are going to be, you can do this programmatically, e.g.:

NSString *key = ... // your app will read the name of the field from the text file
id value = ...      // your app will read the value of the field from the text file

dictionary[key] = value;  // this saves that value for that key in the dictionary

And if you’re using an older version of Xcode (before 4.5), the syntax is:

[dictionary setObject:value forKey:key];