Icon LinkDifferences From Rust

Sway shares a lot with Rust, especially its syntax. Because they are so similar, you may be surprised or caught off guard when they differ. This page serves to outline, from a high level, some of the syntactic gotchas that you may encounter.

Icon LinkEnum Variant Syntax

In Rust, enums generally take one of three forms: unit variants, which have no inner data, struct variants, which contain named fields, and tuple variants, which contain within them a tuple of data. If you are unfamiliar with these terms, this is what they look like:

// note to those skimming the docs: this is Rust syntax! Not Sway! Don't copy/paste this into a Sway program.
 
enum Foo {
	UnitVariant,
	TupleVariant(u32, u64, bool),
	StructVariant {
		field_one: bool,
		field_two: bool
	}
}

In Sway, enums are simplified. Enums variants must all specify exactly one type. This type represents their interior data. This is actually isomorphic to what Rust offers, but with a different syntax. You can see the above enum but with Sway syntax below:

// This is equivalent Sway syntax for the above Rust enum.
enum Foo {
	UnitVariant: (),
	TupleVariant: (u32, u64, bool),
	StructVariant: MyStruct,
}
 
struct MyStruct {
	field_one: bool,
	field_two: bool,
}