Pattern: Builder

The builder pattern is a convenient way to allow mutability when assigning constructor values and then convert to immutable when the final object is constructed.

button(
	color :'color
	text :'string
) { this }

buttonBuilder(
	color = colors.red
	text = ""
	
	setColor(c'color) { 
		color = c
		this
	}
	
	setText(t'string) { 
		text = t
		this
	}
	
	build() {
		button(
			color: color,
			text: text
		)
	}
) { this }

However, if you are primarily using the builder pattern to handle a constructor with many arguments most of which have default values then it is much cleaner to use the default constructor values. They have a special ability to be immutable after construction but mutable during construction:

button(
	color: colors.blue
	text: "Hello"
) { this }

// The color is modified during construction
b: button(color: colors.white)
// This will fail, because the color is actually immutable, it can only be modified during construction
b.color = colors.green