An Aurelia plugin that allows you to create bi-directional BindingFunctions in a similar way to ValueConverters or BindingBehaviors.
In your project install the plugin via jspm
with following command
jspm install npm:aurelia-binding-functions
Make Aurelia load the plugin by adding the following line to the configure
function in the main.js
file of your src
folder
export function configure(aurelia) {
aurelia.use
.standardConfiguration()
.developmentLogging();
+ aurelia.use.plugin('aurelia-binding-functions');
aurelia.start().then(a => a.setRoot());
}
aurelia-binding-functions
should be visible automatically. You may create a BindingFunction the same way as you would BindingBehaviors or ValueConverters.
The simplest implementation for a one-way binding might look as follows:
// async-binding-function.ts //
export class AsyncBindingFunction implements BindingFunction {
connect(callScope: CallScope, binding: Binding, scope: Scope) {
// get the value of the first argument passed to our CallScope,
// e.g. the property from async(property)
const promise = callScope.args[0].evaluate(scope, binding.lookupFunctions, true) as Promise<any> & {promiseResult:any}
// make sure the binding is updated
// once the property "promiseResult" changes on the "promise"
binding.observeProperty(promise, 'promiseResult')
// set the "promiseResult" property once the Promise resolves
if (promise.promiseResult === undefined && typeof promise.then === 'function') {
promise.then(value => {
promise.promiseResult = value
})
}
}
evaluate(callScope: CallScope, scope: Scope, lookupFunctions, mustEvaluate: boolean) {
const promise = callScope.args[0].evaluate(scope, lookupFunctions, true) as Promise<any> & {promiseResult:any}
// return the value of "promiseResult" property
// or undefined if the value of the argument is not set
return promise ? promise.promiseResult : undefined
}
}
Now the BindingFunction can be used inside bindings prefixed by @
, i.e. @async()
:
<require from="./async-binding-function"></require>
<h2>${ @async(somePromise) }</h2>
A BindingFunction can implement the following methods:
export interface BindingFunction {
/**
* invoked by Aurelia to either:
* - retrieve the current value of the binding
* - trigger a call (e.g. by click.delegate)
*/
evaluate(bindingFunctionScope: BindingFunctionScope, scope: Scope, lookupFunctions, mustEvaluate: boolean): any
/**
* invoked if the binding is used as a source of values
* (as opposed to being used to trigger changes, like in click.delegate)
* this is invoked by Aurelia after bind() and every time the binding is recomputed
*/
connect?(bindingFunctionScope: BindingFunctionScope, binding: Binding, scope: Scope): void
/**
* when the binding is two-way, invoked every time new values are fed into the binding by Aurelia
*/
assign?(bindingFunctionScope: BindingFunctionScope, scope: Scope, value: any, lookupFunctions: any): void
/**
* invoked when the binding is bound
*/
bind?(bindingFunctionScope: BindingFunctionScope, binding: Binding, scope: Scope, lookupFunctions: any): void
/**
* invoked when the binding is unbound
*/
unbind?(bindingFunctionScope: BindingFunctionScope, binding: Binding, scope: Scope): void
}
For a one-time binding you only need to implement the evaluate()
method.
A one-way binding will require you to also implement connect()
, while a two-way binding requires you to also implement assign()
.
If you want to create lower-level, global, arbitraitly named Expressions, you may also use ScopeFunctions:
import {ParserImplementation} from 'aurelia-binding';
export function configure(aurelia) {
let parser = aurelia.container.get(ParserImplementation);
parser.registerScopeFunction('@custom', CustomExpression);
}
Where CustomExpression
is a class that implements Expression
.
For references see ast.js.
This library isn't used by Aurelia. It is an optional plugin.
This library can be used in the browser as well as on the server.
To build the code, follow these steps.
Ensure that NodeJS is installed. This provides the platform on which the build tooling runs.
From the project folder, execute the following command:
npm install
Ensure that Gulp is installed. If you need to install it, use the following command:
npm install -g gulp
To build the code, you can now run:
gulp build
You will find the compiled code in the dist
folder, available in three module formats: AMD, CommonJS and ES6.
See gulpfile.js
for other tasks related to generating the docs and linting.
To run the unit tests, first ensure that you have followed the steps above in order to install all dependencies and successfully build the library. Once you have done that, proceed with these additional steps:
Ensure that the Karma CLI is installed. If you need to install it, use the following command:
npm install -g karma-cli
Ensure that jspm is installed. If you need to install it, use the following commnand:
npm install -g jspm
Install the client-side dependencies with jspm:
jspm install
You can now run the tests with this command:
karma start