ImageGear .NET v24.12 - Updated
IPCC.Promise
API Reference > ViewerControl API > IPCC.Promise

Class: Promise

IPCC.Promise()

The IPCC.Promise object is an implementation of the Promises/A+ standard. > "A promise represents the eventual result of an asynchronous operation. The primary > way of interacting with a promise is through its then method, which registers callbacks to receive either > a promise's eventual value or the reason why the promise cannot be fulfilled." > -- [Promises/A+ standard](https://github.com/promises-aplus/promises-spec) The ImageGear.Web Viewing Client API uses Promises as a means for a caller to subscribe callbacks for an asynchronous operation. This API uses promises as an alternative to the pattern of providing callbacks as arguments to the API method. The IPCC.Promise object is compatible with other Promises/A+ implementations, and other non-conformant promise implementations, which are "thenable" (i.e. the promise exposes a `.then()` method).

Constructor

new Promise()

The Promise constructor is for internal use only. Promise objects returned by other API methods are created with this constructor.

Methods

(static) all(promises)

Returns a promise that is fulfilled when all of the input promises are fulfilled. The returned promise is fulfilled with an array of the fulfilment values for all of the input promises. If any of the promises are rejected, then the returned promise will be rejected with the reason of that rejected promise. If rejected, there will be guarantee of the state all promises in the promises array, some have been resolved and some may still be pending.
Parameters:
Name Type Description
promises Array.<(IPCC.Promise|thenable|*)> An array of values that will be resolved. If a value is not a IPCC.Promise object, then this method will create a new IPCC.Promise and fulfill it with the value. Resolution of various types is as follows. - If the item is a IPCC.Promise, then the output value will be the fulfilment value of the promise. - If the item is thenable, then the output value will be the fulfilment value of the thenable. - Otherwise, the output value will be the item.
Throws:
If the `promises` argument is not an array.
Type
TypeError
Example
var viewerControl = $("#myElement").pccViewer(...).viewerControl;

// Get page text for specific pages
IPCC.Promise.all([
    viewerControl.requestPageText(1),
    viewerControl.requestPageText(2)]).then(
    function onFulfilled(values) {
       // Values is an array that contains the text of pages 1 & 2.
       var page1Text = values[0];
       var page2Text = values[1];
    },
    function onRejected(error) {
        alert("Something went wrong getting the page text. " + (error.message ? error.message : error));
    }
);

// Get attributes for all pages
var allPages = _.range(1, viewerControl.getPageCount() + 1); // Using Underscore.js - generates an array like [1, 2, ..., 12]
var pageAttributePromises = _.map(allPages, viewerControl.requestPageAttributes, viewerControl); // Using Underscore.js
IPCC.Promise.all(pageAttributePromises).then(
    function onFulfilled(allPageAttributes) {
        console.log(JSON.stringify(allPageAttributes));
    },
    function onRejected(error) {
        alert("Something went wrong getting the page attributes. " + (error.message ? error.message : error));
    }
);

// it's OK to pass a value that is not a promise
IPCC.Promise.all([
    viewerControl.requestPageAttributes(1),
    true]).then(
    function(values) {
       // Values is an array that contains the text of pages 1 and the value `true`.
       var page1Text = values[0]; // text of page 1
       var otherValue = values[1]; // true
    }
);

then(onFulfilledopt, onRejectedopt) → {IPCC.Promise}

Use `.then(...)` to register callbacks to access the current or eventual value, or reason, of the promise. A promise is in one of three states: pending, resolved, rejected. The `onFulfilled` callback will be called when a promise is resolved, or if a promise is already resolved, then the `onFulfilled` callback will be called immediately. The `onRejected` callback will be called when a promise is rejected, or if a promise is already rejected, then the `onRejected` callback will be called immediately.
Parameters:
Name Type Attributes Description
onFulfilled IPCC.Promise~onFulfilled <optional>
 Called if or when the promise is resolved. Optionally pass a value of `null` or `undefined` if you do not use this callback, but you want to provide an onRejected callback.
onRejected IPCC.Promise~onRejected <optional>
 Called if or when the promise is rejected.
Returns:
A promise object that is resolved according to the Promises/A+ standard.
Type
IPCC.Promise
Example
var viewerControl = $("#myElement").pccViewer(...).viewerControl;

// a basic example
viewerControl.requestPageText(1).then(
    function onFulfilled(value) {
       // according to the definition of requestPageText, the promise will be resolved with the text
       // of the page.
       var pageText = value;
    },
    function onRejected(error) {
        // according to the definition of requestPageText, the promise will be rejected if there is
        // an error extracting text for the document.
        alert("Something went wrong getting the text of page 1. " + (error.message ? error.message : error));
    }
);

// it's OK to pass a value of null (or undefined) for `onFulfilled`
viewerControl.requestPageText(1).then(
    null,
    function onRejected(error) { ... }
);

// it's OK to ignore the onRejected parameter, or pass null or undefined
viewerControl.requestPageText(1).then(
    function onFulfilled(value) { ... }
);

Type Definitions

onFulfilled(value)

An `onFulfilled` callback is called if or when a IPCC.Promise is resolved.
Parameters:
Name Type Description
value * The type and value of the `value` argument depends on the API method that generated the Promise object. See the documentation for the method that generated the Promise.

onRejected(reason)

An `onRejected` callback is called if or when a IPCC.Promise is rejected.
Parameters:
Name Type Description
reason * The type and value of the `reason` argument depends on the API method that generated the Promise object. See the documentation for the method that generated the Promise.

 

 

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