如何在具有不同常量的代码上使用提取方法？

Question

Given I have code like the following:

void foo() {
  String str = "hello";

  a(str, 1);
  b(str, true);

  a(str, 2);
  b(str, false);
}

I would like to extract a new method c like:

void foo() {
  String str = "hello";

  c(str, 1, true);
  c(str, 2, false);
}

However, the automated Extract Method refactoring will only extract one of the a / b pairs. My guess is that it dislikes the differing constants. I can work around this by extracting a local variable first, then extracting the method, then inlining the previously extracted variable, but I still have to find all the instances by hand. With that amount of work, I might as well just make the full change myself when I am looking at each part.

Is there a trick I am missing to let Eclipse know to search a little harder to extract this type of code?

Answer 1

Yes, you need to extract your constants into variable that you can put in the top to tell your tool to pass them as arguments to the extracted method.

void foo() {
  String str = "hello";
  int constant = 1;
  boolean boolValue = true;
  a(str, constant);
  b(str, boolValue);

  constant = 2;
  boolValue = false;
  a(str, constant);
  b(str, boolValue);
}

Doing an extract method should give the following:

public void c(String str, int constant, boolean boolVal){
    a(str, constant);
    b(str, boolVal);
}