add readonly combinator

gcanti · Mar 3, 2017 · 3283f82 · 3283f82
1 parent e56f931
commit 3283f82
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@
 
 - **New Feature**
   - add `partial` combinator
+  - add `readonly` combinator
   - add `never` type
 - **Breaking Changes**
   - remove `undefined` as valid value for `maybe` combinator

diff --git a/src/index.ts b/src/index.ts
@@ -524,6 +524,20 @@ export function tuple<RTS extends Array<Any>>(types: RTS, name?: string): TupleT
   )
 }
 
+export class ReadonlyType<RT extends Any> extends Type<Readonly<TypeOf<RT>>> {
+  constructor(name: string, validate: Validate<Readonly<TypeOf<RT>>>, public readonly type: RT) {
+    super(name, validate)
+  }
+}
+
+export function readonly<RT extends Any>(type: RT, name?: string): ReadonlyType<RT> {
+  return new ReadonlyType(
+    name || `Readonly<${getTypeName(type)}>`,
+    (v, c) => type.validate(v, c).map(x => Object.freeze(x)),
+    type
+  )
+}
+
 export {
   nullType as null,
   undefinedType as undefined,