Remarks

A type-safe builder is a concept, rather than a language feature, so it is not strictly formalized.

A typical structure of a type-safe builder

A single builder function usually consists of 3 steps:

1. Create an object.
2. Execute lambda to initialize the object.
3. Add the object to structure or return it.

Type-safe builders in Kotlin libraries

The concept of type-safe builders is widely used in some Kotlin libraries and frameworks, eg.:

• Anko
• Wasabi
• Ktor
• Spec