Question

I am working on a command-line tool which would run the method

- [NSMutableDictionary setObject:(id)object forKey:(NSString *)key]

The value I want to pass as object is the the content of the string argv[4]… So the user would type:

mytool arg1 arg2 arg3 [NSString stringWithFormat:@"asd"]

Still, plain argv[4] is obviously a char*, so I can’t add that as an object.

Is there a way to turn that string with an object as its content in a plain object so I can pass it on the method above?

Being: Turn "[NSString stringWithFormat:@"asd"]" into [NSString stringWithFormat:@"asd"]?

Note: This applies to any Objective-C object, so I could also pass as argv[4] something like [NSArray arrayWithObjects:@"obj1", nil].

Thanks in advance.

Answer 1

Here’s a brief example of converting C strings into classes and selectors at runtime.

// I added arg5 and arg6 for the example
// mytool arg1 arg2 arg3 NSString stringWithFormat: asd
NSString *className = [[NSString alloc] initWithUTF8String:arg4];
NSString *selectorName = [[NSString alloc] initWithUTF8String:arg5];
NSString *argument = [[NSString alloc] initWithUTF8String:arg6];
Class myClass = NSClassFromString(className);
SEL mySelector = NSSelectorFromString(selectorName);

// If arg5 is a class method
[myClass performSelector:mySelector withObject:argument];
// or if arg5 is an instance method
id instance = [[myClass alloc] init];
[instance performSelector:mySelector withObject:argument];

That’s a simple example with three tokens: NSString, stringWithFormat:, and one argument. To handle more complicated cases, you need to write your own string parser. It shows you some possibilities, though.