Understanding the Problem

The problem presented in the question is related to iOS development and Objective-C programming. The developer wants to create an object based on a string representation of its name, where the first character of the string represents the size and the second character represents the kind of object. For example, if the user chooses an object size of 2 and an object kind of 1, the corresponding object name would be “obj21”.

The question asks for a method called “NSObjectFromString” that can reference an object based on its name as a string, similar to the existing NSSelectorFromString method. However, unlike NSSelectorFromString, which generates a selector (a message send) from a string, “NSObjectFromString” should run a method based on the object’s name.

Objective-C and Dynamic Property Access

In Objective-C, dynamic property access is achieved using the objc_setAssociatedObject and objc_getAssociatedObject methods. These methods allow us to store an object as associated with another object (the one being referenced by its name) in a dictionary-like structure called an association.

To achieve our goal, we can create a class that implements this association mechanism. This class will act as a mediator between the names and the objects they represent. It will use dynamic property access to store the objects in a dictionary and retrieve them based on their associated names.

The NSObjectFromString Class

Here’s an example implementation of the NSObjectFromString class:

{
    {< highlight Objective-C >}
    @interface NSObjectFromString : NSObject

    - (instancetype)initWithName:(NSString *)name;
    
    // Method to set and get objects based on their associated names
    
   @end
}

The above code defines a new class NSObjectFromString that inherits from NSObject. The initWithName: method is used to initialize the object with a given name. This name will serve as the key in our association dictionary.

Association Dictionary

We’ll create an instance variable called associationDictionary to store our objects:

{
    {< highlight Objective-C >}
    @private
    NSDictionary *_associationDictionary;

    - (instancetype)initWithName:(NSString *)name {
        self = [super init];
        if (self) {
            _associationDictionary = [[NSMutableDictionary alloc] init];
        }
        return self;
    }

    // Method to add an object to the association dictionary based on its name
    
    - (void)setObject:(id)object forName:(NSString *)name {
        [_associationDictionary setObject:object forKey:name];
    }
    
    // Method to retrieve an object from the association dictionary based on its associated name
    
    - (id)getObjectForName:(NSString *)name {
        return [_associationDictionary objectForKey:name];
    }

   @end
}

The associationDictionary is initialized in the initWithName: method and used by other methods of the class to store and retrieve objects.

Using NSObjectFromString

To use our NSObjectFromString class, we need to create an instance of it with a given name. We can then call methods like setObject:forName: and getObjectForName: to add or retrieve objects from the association dictionary.

{
    {< highlight Objective-C >}
    NSObjectFromString *obj = [[NSObjectFromString alloc] initWithName:@"obj21"];
    
    // Add an object to the association dictionary based on its name
    
    id obj1 = @[@"someValue", @"someArray"];
    [obj setObject:obj1 forKey:@"obj21"];
    
    // Retrieve an object from the association dictionary based on its associated name
    
    id retrievedObj = [obj getObjectForName:@"obj21"];
    NSLog(@"%@", retrievedObj);  // prints "[someValue, someArray]"
    
   @end
}

In this example, we create a new instance of NSObjectFromString with the name “obj21”. We then add an object to the association dictionary using setObject:forName:. Finally, we retrieve the object from the association dictionary using getObjectForName: and log its contents.

Conclusion

The provided code snippet illustrates how you can create a class called NSObjectFromString that allows for dynamic property access based on a string representation of an object’s name. The class uses an association mechanism to store objects in a dictionary-like structure, where the names serve as keys. This approach provides a flexible way to reference objects dynamically.

While this solution does not directly achieve the functionality described by NSSelectorFromString, it offers a useful alternative for managing dynamic relationships between objects and their associated properties in Objective-C-based applications.

Keep in mind that this class can be further extended or customized based on your specific needs. It is essential to evaluate whether using such an approach aligns with the requirements of your project, considering factors like performance, maintainability, and scalability.

Last modified on 2025-01-28