Deferred 编辑

A Deferred object is returned by the PromiseUtils.defer() method to provide a new promise along with methods to change its state.

Method overview

void resolve([optional] aValue);

void reject([optional] aReason);

Properties

Attribute	Type	Description
promise Read only	Promise	A newly created promise, initially in the pending state.

Methods

resolve()

Fulfills the associated promise with the specified value, or propagates the state of an existing promise. If the associated promise has already been resolved, either to a value, a rejection, or another promise, this method does nothing.

Note: This function is exactly same as Promise constructor's resolve argument, and can be called with any value of this. Note: Calling this method with a pending promise as the aValue argument, and then calling it again with another value before the promise is resolved or rejected, will have no effect the second time, as the associated promise is already resolved to the pending promise value as its resolution.

void resolve(
  aValue
);

Parameters

aValue Optional

If this value is not a promise, including undefined, it becomes the fulfillment value of the associated promise. If this value is a promise, then the associated promise will be resolved to the passed promise, and follow the state as the provided promise (including any future transitions).

reject()

Rejects the associated promise with the specified reason. If the promise has already been resolved, either to a value, a rejection, or another promise, this method does nothing.

Note: This function is exactly same as Promise constructor's reject argument, and can be called with any value of this.

void reject(
  aReason
);

Parameters

aReason Optional

The rejection reason for the associated promise. Although the reason can be undefined, it is generally an Error object, like in exception handling.

Note: This argument should not be a promise. Specifying a rejected promise would make the rejection reason equal to the rejected promise itself, and not its rejection reason.

See also

• PromiseUtils.jsm
• DOM Promise