Named-argument syntax makes Kotlin calls clearer by writing parameter names beside their values. It is especially useful when several arguments share a type or represent Boolean choices. section 3.2.1
Making a collection call readable
A positional call can hide which value means what: joinToString(collection, " ", " ", ".") Kotlin makes the parameters explicit: joinToString(collection, separator = " ", prefix = " ", postfix = ".") You may name only selected arguments. When every argument is named, you may also reorder them: joinToString( postfix = ".", separator = " ", collection = collection, prefix = " " ) section 3.2.1
Use named arguments to:
- Expose the meaning of arguments in calls with many parameters. section 3.2.1
- Combine explicit names with default parameter values, omitting values that do not need customization. section 3.2.1
- Construct objects clearly, as in Person("Alice", age = 29), while leaving omitted parameters at their defaults. section 1.1
- Apply Kotlin annotations with explicit constructor parameter names; Java annotations require names for specified attributes except value. section 12.1.4
- Keep argument names synchronized after parameter renaming through IDE refactoring actions. section 3.2.1
joinToString(collection, separator = " ", prefix = " ", postfix = ".")
Compare a positional joinToString call with its named-argument form. section 3.2.1
