result builder transform

Swift ⟩ Attributes ⟩ Result Builders ⟩

⭐️ 重點

Can’t use break, continue, defer, guard(👉 ❓), return, while, do-catch in the code (usaully the body of a closure) that a result builder transforms.

• The transformation process doesn’t change declarations in the code, which lets you use temporary constants and variables to build up expressions piece by piece.

• It also doesn’t change throw statements, compile-time diagnostic statements, or closures that contain a return statement.

An assignment (=) statement is transformed like an expression, but is understood to evaluate to (). You can define an overload of buildExpression(_:) that takes an argument of type () to handle assignments specifically. 👉 Swift Reference

📘 手冊