Lecture
The logic of conditional execution tends to become complicated, so a number of refactorings are intended to simplify it.
Splitting a conditional statement
Problem: You have a complex conditional statement (if-then / else or switch).
Solution: Select into separate methods all complex parts of the operator: condition, then and else.
Combining conditional statements
Problem: You have several conditional statements leading to the same result or action.
Solution: Combine all the conditions in one conditional statement.
Merging duplicate fragments in conditional statements
Problem: The same code fragment is in all branches of the conditional operator.
Solution: Move it beyond the operator.
Remove control flag
Problem: You have a boolean variable that plays the role of a control flag for several boolean expressions.
Solution: Use break, continue and return instead of this variable.
Replacing nested conditional operators with a boundary operator
Problem: You have a group of nested conditional statements, among which it is difficult to distinguish the normal course of code execution.
Solution: Select all the checks for special or boundary cases of execution in separate conditions and place them in front of the main checks. Ideally, you should get a “flat” list of conditional statements, one after another.
Replacing a Conditional Operator with Polymorphism
Problem: You have a conditional statement that, depending on the type or properties of the object, performs various actions.
Solution: Create subclasses with which the branches of the conditional operator correspond. In them, create a common method and move the code into it from the corresponding branch of the conditional operator. Subsequently, replace the conditional operator with a call to this method. Thus, the desired implementation will be selected through polymorphism, depending on the class of the object.
Introducing a Null Object
Problem: Due to the fact that some methods return null instead of real objects, you have many null checks in your code.
Solution: Instead of null, return a Null object that provides default behavior.
Introduction of Approval Verification
Problem: The correct operation of the code section assumes the presence of some specific conditions or values.
Solution: Replace these assumptions with specific tests.
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