Indirect Inputs: These are often object state. Before you begin working with your arguments, check that they are valid with require. Maybe you need an Int to be non-negative. Capture Assumptionsĭirect Inputs: These are function arguments. Examples of using each alone, then all together, will make that clear. These three functions look very similar, but each has its specific purpose. Use that message to jumpstart debugging by reporting relevant values. So each function has another variation.That variation takes a lazy message closure as final argument. If you do not use these functions, you will probably reinvent them.īare exceptions and errors are little help. These functions give Kotlin programmers a common language. Use it to clarify outcomes and check your work. assert(Boolean) throws AssertionError when its argument is false (but only if JVM assertions are enabled with -ea).check(Boolean) throws IllegalStateException when its argument is false.require(Boolean) throws IllegalArgumentException when its argument is false.

Kotlin has three functions for capturing execution context: You will catch any bugs sooner, and you will spend less time debugging. Mastering Kotlin’s common language for codifying your functions’ assumptions and promises will help you write code you can change with confidence. At a glance, you can see what it needs to succeed, and what happens when it does.

Kotlin by lazy with parameter