Do you know about method swizzling?
Method swizzling is a clever approach in object-oriented programming that enables us to modify or expand the functionality of a method by intercepting its original implementation and replacing it with a new one. It proves to be incredibly handy when we wish to include extra features, logging, or pre/post-processing to existing methods without altering the initial source code.
Let's explore an example in TypeScript where we showcase method swizzling by capturing the doSomething method of a parent abstract class and incorporating an additional action before executing the original implementation:
abstract class AbstractClass {
abstract doSomething(): void;
constructor() {
const originalDoSomething = this.doSomething.bind(this);
this.doSomething = function() {
console.log('Performing additional action before doSomething');
// Insert any additional logic here
// Call the original implementation
return originalDoSomething();
};
}
}
class MyClass extends AbstractClass {
doSomething() {
console.log('Original doSomething implementation');
// Original doSomething logic here
}
}
const myInstance = new MyClass();
myInstance.doSomething();
In this provided script, the AbstractClass contains an abstract method called doSomething. The method swizzling process takes place within the constructor of AbstractClass. We retain the original implementation of doSomething in originalDoSomething and then set a new wrapper function to this.doSomething, which executes the additional action prior to calling the original implementation.
The MyClass class inherits from AbstractClass and includes its own version of the doSomething method.
To conclude, we initiate an instance of MyClass and trigger the doSomething method. Consequently, the swizzling mechanism defined in the AbstractClass constructor comes into play, running both the added action and the original implementation.
Feel free to adapt the logging and extra action logic as per your specific needs. Method swizzling provides tremendous flexibility in enhancing existing methods while preserving the cleanliness and manageability of the codebase.