Extract method
The Extract Method refactoring lets you take a code fragment that can be grouped, move it into a separated method, and replace the old code with a call to the method.
When you extract the method you need to check for variables. If there is one output variable, it is used as a return value for the extracted method. In case there are multiple output variables, the Extract Method refactoring may not be applied, and the error message appears.
There are several workarounds to allow Extract Method work in this case. For example, you may introduce a special data-class that contains all output values.
Extract method
Select a code fragment you want to extract to a method.
Press Ctrl+Alt+M or go to in the main menu.
If Aqua detects code that is only partially duplicated, it suggests extracting a parameter to proceed with the refactoring.
Example
Let's extract the a+b expression into a method (function for Kotlin), and replace duplicates .
Before | After |
|---|---|
public void method() {
int a=1;
int b=2;
int c=a+b;
int d=a+c;
}
|
public void method() {
int a=1;
int b=2;
int c=add(a,b);
int d=add(a,c);
}
...
private int add(int a, int b) {
return a+b;
}
|
Before | After |
|---|---|
fun method(){
val a = 1
val b = 2
val c = a + b
val d = a + b
}
|
fun method(){
val a = 1
val b = 2
val c = add(a, b)
val d = add(a, b)
}
private fun add(a: Int, b: Int) = a + b
|
Code examples
Before | After |
|---|---|
private func setupUI() {
// ...
// This code will be extracted to a method
self.buttonLogin.layer.borderColor = UIColor.black.cgColor
self.buttonLogin.layer.borderWidth = 1.0
self.buttonLogin.setTitleColor(UIColor.black, for: .normal)
self.buttonLogin.setTitle("Login", for: .normal)
}
|
private func setupUI() {
// ...
// Extracted method's call
setupLoginButton()
}
// Extracted method
private func setupLoginButton() {
self.buttonLogin.layer.borderColor = UIColor.black.cgColor
self.buttonLogin.layer.borderWidth = 1.0
self.buttonLogin.setTitleColor(UIColor.black, for: .normal)
self.buttonLogin.setTitle("Login", for: .normal)
}
|
Before | After |
|---|---|
- (void)setupUI {
// ...
// This code will be extracted to a method
self.buttonLogin.layer.borderColor = [[UIColor blackColor] CGColor];
self.buttonLogin.layer.borderWidth = 1.0;
[self.buttonLogin setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[self.buttonLogin setTitle:@"Login" forState:UIControlStateNormal];
}
|
- (void)setupUI {
// ...
// Extracted method's call
[self setupLoginButton];
}
// Extracted method
- (void)setupLoginButton {
self.buttonLogin.layer.borderColor = [[UIColor blackColor] CGColor];
self.buttonLogin.layer.borderWidth = 1.0;
[self.buttonLogin setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[self.buttonLogin setTitle:@"Login" forState:UIControlStateNormal];
}
|