Replace Parameter with Method Call

You invoke a method, then pass the result as a parameter.

“The receiver can also invoke this method.”

Don’t pass what the receiver can get itself.

graph LR
    A[Client gets X, calls Func(X)] -->|Refactoring| B[Client calls Func(), Func gets X]

When to apply (Smells)

  • Long Parameter List: Passing data that the method could easily fetch.

Motivation

  • Simplicity: Reduce the work the caller has to do.

Mechanics (Steps)

  1. In the method, call the other method directly.
  2. Remove the parameter.

Explanation

Problem

price = quantity * itemPrice; discount = getDiscount(price);

Solution

Inside getDiscount(): price = quantity * itemPrice; ... Caller: discount = getDiscount();

Pros and Cons

Pros Cons
  • Simpler calls
    		•
  • Coupling (Method now depends on other methods)
    		•

    Code example

    Typescript

    Before

    After

    PHP

    Before

    After