Merge pull request #2 from joshuajaco/add-match

Add match method

index.ts

@@ -10,6 +10,10 @@ type Methods<T, E> = {
   andThen: <U>(fn: (value: T) => Result<U, E>) => Result<U, E>;
   or: <F>(result: Result<T, F>) => Result<T, F>;
   orElse: <F>(fn: (error: E) => Result<T, F>) => Result<T, F>;
+  match: <U, F>(matcher: {
+    ok: (value: T) => U;
+    error: (error: E) => F;
+  }) => U | F;
 };
 
 type Attributes<T, E> = { ok: true; value: T } | { ok: false; error: E };
@@ -63,6 +67,10 @@ function createResult<T, E>(init: Attributes<T, E>): Result<T, E> {
       if (init.ok) return createResult(init);
       return createResult({ ok: false, error: fn(init.error) });
     },
+    match(matcher) {
+      if (init.ok) return matcher.ok(init.value);
+      return matcher.error(init.error);
+    },
   };
 }
 

package.json

@@ -27,6 +27,7 @@
     "nyc": "^15.1.0",
     "prettier": "^2.7.1",
     "rimraf": "^3.0.2",
+    "ts-expect": "^1.3.0",
     "typescript": "^4.7.4"
   }
 }

test.ts

@@ -1,5 +1,6 @@
-import { Result } from "./index";
 import assert from "assert";
+import { expectType } from "ts-expect";
+import { Result } from "./index";
 
 const { ok, error, equals, from, wrap } = Result;
 
@@ -184,3 +185,14 @@ assert(equals(ok<number, number>(2).orElse(err).orElse(sq), ok(2)));
 assert(equals(error<number, number>(3).orElse(sq).orElse(err), ok(9)));
 
 assert(equals(error<number, number>(3).orElse(err).orElse(err), error(3)));
+
+// match
+
+assert.equal(ok(1).match({ ok: (x) => x.toString(), error: () => {} }), "1");
+assert.equal(error(1).match({ ok: () => {}, error: (x) => x.toString() }), "1");
+
+expectType<number>(ok(1).match({ ok: () => 1, error: () => 1 }));
+expectType<"foo" | "bar">(ok(1).match({ ok: () => "foo", error: () => "bar" }));
+
+// @ts-expect-error
+expectType<string>(ok(1).match({ ok: () => "foo", error: () => {} }));