Extensions vs member functions priority in Kotlin - Quick Revision & Key Differences

Recall & Review

beginner

What happens when a Kotlin class has both a member function and an extension function with the same name?

The member function always has higher priority and will be called instead of the extension function.

beginner

Can extension functions override member functions in Kotlin?

No, extension functions cannot override member functions. Member functions take precedence even if an extension function has the same signature.

intermediate

Why do member functions have priority over extension functions in Kotlin?

Because member functions are part of the class definition and have direct access to the class internals, Kotlin always prefers them over extensions which are resolved statically.

intermediate

How are extension functions resolved in Kotlin?

Extension functions are resolved statically based on the declared type of the variable, not the runtime type.

beginner

What is a practical use case for extension functions despite member functions having priority?

Extension functions allow adding new functionality to classes without modifying their source code, especially useful for classes from libraries or the Kotlin standard library.

In Kotlin, if a class has a member function and an extension function with the same name, which one is called?

A Both are called

B The member function

C The extension function

D It causes a compile error

Member functions have higher priority and are called instead of extension functions with the same name.

Can extension functions override existing member functions in Kotlin?

A Only for open classes

B Only if marked with override

C Yes, always

D No, extension functions cannot override member functions

Extension functions cannot override member functions; member functions always take precedence.

How are extension functions resolved in Kotlin?

A Statically based on the variable's declared type

B By the JVM bytecode

C Based on the object's runtime type

D Dynamically at runtime

Extension functions are resolved statically using the declared type of the variable.

Why might you use an extension function in Kotlin?

A To add functionality to a class without modifying it

B To override a member function

C To change the class's internal state

D To create a new class

Extension functions let you add new functions to classes without changing their source code.

If a variable is declared as a superclass type but holds a subclass instance, which extension function is called?

A Extension function of the subclass

B Member function of the subclass

C Extension function of the superclass

D No extension function is called

Extension functions are resolved based on the declared type, so the superclass extension function is called.

Explain the priority between member functions and extension functions in Kotlin and why it matters.

Think about how Kotlin decides which function to call when names clash.

Describe how extension functions are resolved in Kotlin and how this affects their behavior compared to member functions.

Consider the difference between compile-time and runtime decisions.