chain

Transforms the value and context of a Result computation with an unary function. As with .map(), the transformation is only applied if the value is an Ok, but the transformation is expected a new Result value, which then becomes the result of the method.

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).((b) => Result a c) => Result a c

Documentation

Example:

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

const divideBy = (a) => (b) =>
  a === 0        ?  Result.Error('division by zero')
: /* otherwise */   Result.Ok(b / a);


Result.Ok(4).chain(divideBy(2));
// ==> Result.Ok(2)

Result.Error(4).chain(divideBy(2));
// ==> Result.Error(4)

Result.Ok(4).chain(divideBy(0));
// ==> Result.Error('division by zero')

Properties

Source Code

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

{
    /*~*/
    Error: function chain(f) {
      assertFunction('Result.Error#chain', f);
      return this;
    },

    /*~*/
    Ok: function chain(f) {
      assertFunction('Result.Ok#chain', f);
      return f(this.value);
    }
  }