apply

Applies the function contained in one Result to the value in another Result. Application only occurs if both Results are Ok, otherwise keeps the first Error.

This feature is experimental!

This API is still experimental, so it may change or be removed in future versions. You should not rely on it for production applications.

Signature

Type(what is this?)

forall a, b, c:
  (Result a ((b) => c)).(Result a b) => Result a c

Documentation

Applies the function contained in one Result to the value in another Result. Application only occurs if both Results are Ok, otherwise keeps the first Error.

Note that Result.Ok(x => x + 1).apply(Result.Ok(1)) is equivalent to Result.Ok(1).map(x => x + 1).

Example:

const Result = require('folktale/result');

function increment(value) {
  return value + 1;
}

Result.Ok(increment).apply(Result.Ok(1));
// ==> Result.Ok(2)

Result.Ok(increment).apply(Result.Error(1));
// ==> Result.Error(1)

Result.Error(increment).apply(Result.Ok(1));
// ==> Result.Error(increment)

Result.Error(increment).apply(Result.Error(1));
// ==> Result.Error(increment)

Properties

Source Code

Defined in source/result/result.js at line 75, column 19

{
    /*~*/
    Error: function apply(anResult) {
      assertResult('Result.Error#apply', anResult);
      return this;
    },

    /*~*/
    Ok: function apply(anResult) {
      assertResult('Result.Ok#apply', anResult);
      return anResult.map(this.value);
    }
  }