registerConverter

function

`stache.registerConverter(converterName, getterSetter)`

Creates a helper that can do two-way conversion between two values. This is especially useful with {($two-way)} bindings like:

<input {($value)}='numberToString(~age)'/>

A converter helper provides:

a get method that returns the value of the left value given the arguments passed on the right.
a set method that updates one or multiple of the right arguments computes given a new left value.

numberToString might converts a number (age) to a string (value), and the string (value) to a number (age) as follows:

stache.registerConverter("numberToString", {
 get: function(fooCompute) {
    return "" + fooCompute();
 },
 set: function(newVal, fooCompute) {
    fooCompute(+newVal);
 }
});

Parameters

converterName {String}:
The name of the converter helper.
getterSetter {getterSetter}:
An object containing get() and set() functions.

Use

These helpers are useful for avoiding creating can-define/map/map getters and setters that do similar conversions on the view model. Instead, a converter can keep your viewModels more ignorant of the demands of the view. Especially as the view's most common demand is that everything must be converted to a string.

That being said, the following is a richer example of a converter, but one that should probably be part of a view model.

<input {($value)}='fullName(~first, ~last)'/>

The following might converts both ways first and last to value.

var canBatch = require("can-event/batch/batch");

stache.registerConverter("fullName", {
 get: function(first, last) {
    return first() + last();
 },
 set: function(newFullName, first, last) {
    canBatch.start();
    var parts = newFullName.split(" ");
    first(parts[0]);
    last(parts[1]);
    canBatch.stop();
 }
});