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Introduce Parameter Object

Consolidating parameters in a single class, freeing the other methods from this code.

 The Introduce Parameter Object refactoring technique is used to replace multiple parameters in a method with a single parameter object, in order to improve the readability and maintainability of the codebase. This can be useful when a method has a large number of parameters, making it difficult to understand or maintain.

 Introduce Parameter can be likened to an obsession with primitives in that it helps to break down hard-coded values or expressions into smaller, more manageable pieces.

 For example, consider the following method, which has several parameters:

class Order {

 calculateTotal(subtotal, taxRate, shippingCost, discount) {

  const tax = subtotal * taxRate;

  const total = subtotal + tax + shippingCost - discount;

  return total;

 }

}

 To improve the readability and maintainability of this method, we can replace the multiple parameters with a single parameter object called pricingInfo:

class Order {

 calculateTotal(pricingInfo) {

  const tax = pricingInfo.subtotal * pricingInfo.taxRate;

  const total = pricingInfo.subtotal + tax + pricingInfo.shippingCost - pricingInfo.discount;

  return total;

 }

}

 In this example, we have replaced the multiple parameters with a single parameter object called pricingInfo. This improves the readability of the calculateTotal method by reducing the number of parameters it takes and making it clear that it's calculating the total of an order. It also makes the method more flexible as it can now be used with different pricing information, depending on the context in which it is called. This can be useful in situations where the pricing information varies by region or changes over time.

 Another benefit of this technique is that it allows for reusing the method in different parts of the codebase without changing its implementation. For example, in the above example, if we have another method that also needs to calculate the total of an order with different pricing information, we can simply pass the pricingInfo object when calling the method, instead of duplicating the calculation logic.


 In summary, Introduce Parameter Object refactoring technique is used to replace multiple parameters in a method with a single parameter object, in order to improve the readability and maintainability of the codebase. It can be useful when a method has a large number of parameters, making it difficult to understand or maintain. Additionally, it allows for reusing the method in different parts of the codebase without changing its implementation.