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fix(maybe): map func should return NonNullable<R> #149

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Merged
merged 1 commit into from
May 21, 2020
Merged

fix(maybe): map func should return NonNullable<R> #149

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2 changes: 1 addition & 1 deletion src/maybe/maybe.interface.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ export interface IMaybe<T> extends IMonad<T> {
/**
* Map output of non-empty data to a new value
*/
map<R>(f: (t: T) => R): IMaybe<R>
map<R>(f: (t: T) => NonNullable<R>): IMaybe<R>

/**
* Returns true if value is not empty
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5 changes: 3 additions & 2 deletions src/maybe/maybe.spec.ts
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Expand Up @@ -199,14 +199,15 @@ describe('Maybe', () => {
const maybeNotSomeSome2 = maybe(sut)
.map(_str => getUserService<string>(0))
.valueOr('fallback')

const maybeNotSomeSome3 = maybe(sut)
.map(_str => getUserService<string>(''))
.map(_str => 'sut')
.valueOr('fallback')

expect(maybeSomeString).toEqual('initial input mapped')
expect(maybeNotSomeSomeString).toEqual('fallback')
expect(maybeNotSomeSome2).toEqual(0)
expect(maybeNotSomeSome3).toEqual('')
expect(maybeNotSomeSome3).toEqual('sut')
})

it('should handle undefined input', () => {
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4 changes: 2 additions & 2 deletions src/maybe/maybe.ts
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Expand Up @@ -74,7 +74,7 @@ export class Maybe<T> implements IMaybe<T> {
: [this.value as NonNullable<T>]
}

public map<R>(fn: (t: NonNullable<T>) => R): IMaybe<R> {
public map<R>(fn: (t: NonNullable<T>) => NonNullable<R>): IMaybe<R> {
return this.isSome()
? new Maybe<R>(fn(this.value as NonNullable<T>))
: new Maybe<R>()
Expand All @@ -98,7 +98,7 @@ export class Maybe<T> implements IMaybe<T> {
: new Maybe<T>()
}

public apply<R>(fab: IMaybe<(v: T) => R>): IMaybe<R> {
public apply<R>(fab: IMaybe<(v: T) => NonNullable<R>>): IMaybe<R> {
return this.flatMap(b => fab.map(fn => fn(b)))
}
}