Add map() methods for Result instances

joanllenas · May 17, 2019 · d7b9e8b · d7b9e8b
1 parent b8b2ea6
commit d7b9e8b
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Showing 2 changed files with 11 additions and 2 deletions.
diff --git a/src/json-decoder.spec.ts b/src/json-decoder.spec.ts
@@ -10,14 +10,15 @@ const expectOkWithValue = <a>(result: Result<a>, expectedValue: a) =>
  expect(result)
  .to.be.an.instanceof(Ok)
  .and.to.deep.equal({
- value: expectedValue
+ value: expectedValue,
+ map: Ok.prototype.map
  });
 const expectErr = <a>(result: Result<a>) =>
  expect(result).to.be.an.instanceof(Err);
 const expectErrWithMsg = <a>(result: Result<a>, expectedErrorMsg: string) =>
  expect(result)
  .to.be.an.instanceof(Err)
- .and.to.deep.equal({ error: expectedErrorMsg });
+ .and.to.deep.equal({ error: expectedErrorMsg, map: Err.prototype.map });
 
 // Tests
 describe('json-decoder', () => {

diff --git a/src/result.ts b/src/result.ts
@@ -1,8 +1,16 @@
 export class Ok<a> {
  constructor(readonly value: a) {}
+
+ map<b>(fn: (a: a) => b): Result<b> {
+ return ok(fn(this.value));
+ }
 }
 export class Err {
  constructor(readonly error: string) {}
+
+ map<b>(fn: (a: any) => b): Result<b> {
+ return this;
+ }
 }
 export type Result<a> = Ok<a> | Err;