Fetch Plugin API

The Fetch Plugin API provides a way for modules to hook into the request flow of API traffic coming to and from the Form.io Renderer and Builder. The following provides the documentation for this plugin.
Plugin methods
Formio.registerPlugin(plugin, [name])
Registers a plugin with Formio.js. An optional name parameter can be provided to be used with Formio.getPlugin().
A plugin must be an object, and can have any of the following optional properties:
priority: The priority of the plugin relative to other plugins that determines call order. Higher numbers have higher priority. If not specified it will default to a priority of 0.
init: An initialization function called when registered with Formio. It will receive the global Formio object as its first parameter.
deregister: A deregistration function called when deregistering with Formio. It will receive the global Formio object as its first parameter.
See below on using hooks in your plugin.
Formio.getPlugin(name)
Returns the plugin registered with the given name.
Formio.deregisterPlugin(plugin)
Deregisters a plugin with Formio.js. It will call the deregister function on the plugin before deregistering. The plugin argument can be the instance of the plugin or the optional name given when registered. Returns true if the plugin was successfully deregistered, false if the plugin does not exist.
Formio.events
This is an EventEmitter that you may use as an event publish/subscribe system in your plugins.
Plugin hooks
Plugins can provide hooks that are invoked at different points in the library. To use a particular hook below, add a function to your plugin with the same name as the hook.
The following are the currently available hooks.
preRequest(requestArgs)
Called before a request. If you return a promise, Formio.js will wait for it to resolve before starting the request.
requestArgs is an object that contains the following properties:
formio: The Formio instance calling the request.
type: The type of resource being requested (ex: form, forms, submission).
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
opts: Any opts given to the request
request(requestArgs)
Called before a request, and gives plugins a chance fulfill the request before it is sent. If you return a non-null, non-undefined value (or a promise that resolves to one), that will be used as the results of the request instead of making the default network request.
Only the first highest priority that returns a value will replace the contents. Your plugin's hook will not be called if a higher priority plugin returns a value.
requestArgs is an object that contains the following properties:
formio: The Formio instance calling the request.
type: The type of resource being requested (ex: form, forms, submission).
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
opts: Any opts given to the request
wrapRequestPromise(promise, requestArgs)
Called when a request is made and gives plugins access to the promise that is returned when a user makes a request. The promise that is returned from this hook will be returned to the user. You may wrap the original promise or extend the promise chain with this hook. (You must return a promise that uses the original promise, or the promise returned to users will not resolve as expected).
promise is the promise of the request.
requestArgs is an object that contains the following properties:
formio: The Formio instance calling the request.
type: The type of resource being requested (ex: form, forms, submission).
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
opts: Any opts given to the request
preStaticRequest(requestArgs)
Same as preRequest hook but used for requests that use the global Formio object instead of a Formio instance. This includes functions like Formio.loadProjects(), Formio.availableActions(), Formio.currentUser().
requestArgs is an object that contains the following properties:
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
staticRequest(requestArgs)
Same as request hook but used for requests that use the global Formio object instead of a Formio instance. This includes functions like Formio.loadProjects(), Formio.availableActions(), Formio.currentUser().
requestArgs is an object that contains the following properties:
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
wrapStaticRequestPromise(promise, requestArgs)
Same as wrapRequestPromise hook but used for requests that use the global Formio object instead of a Formio instance. This includes functions like Formio.loadProjects(), Formio.availableActions(), Formio.currentUser().
promise is the promise of the request.
requestArgs is an object that contains the following properties:
url: The url being requested.
method: The HTTP request method.
data: The HTTP request body, if any.
Example Plugin
This example plugin will delay all requests by 5 seconds
plugins/fetch.js
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export const DelayPlugin = {
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  priority: 0,
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  preRequest: function(requestArgs) {
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    return new Promise(function(resolve, reject){
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      setTimeout(resolve, 5000);
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    })
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  }
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}
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module.js
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import { DelayPlugin } from './plugins/fetch';
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export default {
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    fetch: DelayPlugin
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}
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