Why Custom result builder declaration in Swift? - Purpose & Use Cases

The Big Idea

What if you could write complex code as simply as telling a story?

The Scenario

Imagine you want to create a complex user interface or build a structured data format by writing many nested function calls or manual object creations.

It feels like stacking blocks one by one without any help to organize or simplify the process.

The Problem

Manually writing all the nested calls or object creations is slow and confusing.

You often make mistakes with commas, brackets, or order, and the code becomes hard to read and maintain.

The Solution

Custom result builders let you write code in a clear, natural way that looks like a simple list or block.

The builder automatically transforms your code into the complex structure behind the scenes, saving time and reducing errors.

Before vs After

✗ Before

let view = VStack { Text("Hello") Text("World") }

✓ After

@resultBuilder struct MyBuilder { ... } MyBuilder.build { Text("Hello") Text("World") }

What It Enables

It enables writing clean, readable, and expressive code that feels like natural language but builds complex results automatically.

Real Life Example

SwiftUI uses custom result builders to let you design user interfaces by simply listing views inside braces, making UI code easy and fun to write.

Key Takeaways

Manual nested code is hard and error-prone.

Custom result builders simplify complex code into clear blocks.

They make your code easier to read, write, and maintain.