Custom result builder declaration in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom result builder in Swift?

A custom result builder is a special type that lets you create a DSL (Domain Specific Language) by combining multiple statements into a single result, using a clean and readable syntax.

beginner

Which attribute do you use to declare a custom result builder in Swift?

You use the @resultBuilder attribute before a struct or enum to declare it as a custom result builder.

intermediate

Name two required static methods a custom result builder must implement.

The two required static methods are buildBlock(_ components: Component...) and buildExpression(_ expression: Expression). These combine parts of the DSL into a final result.

beginner

What does the buildBlock method do in a custom result builder?

It combines multiple components into one result. Think of it like putting puzzle pieces together to form the final picture.

intermediate

How can you handle optional statements inside a custom result builder?

You implement the buildOptional(_ component: Component?) method to handle optional parts, like if statements that might or might not add content.

What keyword do you use to mark a type as a custom result builder in Swift?

A @dslBuilder

B @builder

C @customBuilder

D @resultBuilder

The correct attribute is @resultBuilder to declare a custom result builder.

Which method combines multiple components into one in a custom result builder?

A buildBlock

B buildFinal

C buildOptional

D buildExpression

buildBlock combines multiple components into a single result.

How do you handle optional content inside a custom result builder?

A buildExpression

B buildOptional

C buildIf

D buildBlock

The buildOptional method handles optional components like if statements.

What is the main purpose of a custom result builder?

A To simplify combining multiple statements into one result

B To create a new data type

C To improve performance

D To handle errors automatically

Custom result builders simplify combining multiple statements into a single, readable result.

Which of these is NOT a typical method in a custom result builder?

A buildOptional

B buildExpression

C buildClass

D buildBlock

buildClass is not a method used in custom result builders.

Explain how to declare and use a custom result builder in Swift.

Think about how you create a mini language inside Swift using special methods.

Describe how optional and conditional statements are handled inside a custom result builder.

Consider how if statements might add or skip parts in the final result.