fluid-binder

This package provides a mechanism for binding Fluid view component model variables to DOM elements using selectors.

You can bind to any DOM element whose value can be read and set using fluid.value, but the primary (and tested) use case is binding model variables to form elements, specifically:

• text <input> fields
• radio <input> fields
• checkbox <input> fields
• <textarea> fields
• <select> fields

Once you run fluid.binder.applyBinding(component) (see "Static Functions" below), a binding is created between any selectors and model variables referenced inoptions.binding (see "Supported options" for the format).

Once a binding exists, changes to a bound model sent using the change applier are used to update the DOM element's value.

The binding is bidirectional. Change events to a bound DOM element's value are also relayed to the associated model variable. Note that change events are not generated when you directly set the element's value, but only when you have updated the value using browser events and change focus. For more details, see the jQuery documentation for the change event.

Supported options

The fluid.binder.applyBinding function provided by this package can only do its work if you have the following options defined:

Option	Type	Description
selectors	{Object}	You must define one or more selectors that can be used in a binding.
bindings	{Object}	Defines the relationship between selectors and model variables. The full notation for this option is outlined below.

Long notation

There are two ways of specifying bindings. The "long form" has named keys (as in the first example above) and supports the following options:

• selector: A valid selector for your component. Must be able to be resolved using that.locate(selector)
• path: A valid path for the model variable whose value will be watched. Must be able to be resolved using fluid.get(that.model, path).
• rules.domToModel: Model transformation rules that are applied to a DOM (element) value before it is relayed to the model.
• rules.modelToDom: Model transformation rules that are applied to a model value before it is relayed to the DOM (element).

The "long form" looks like:

bindings: {
    "<key>": {
        selector: "<selector1>",
        path:     "<path1>"
    }
}

Example 1: Using "long notation" to handle a numeric model value.

The following is an example of how model transformation rules are used in binding definitions:

bindings: {
    "myKey": {
        selector: "mySelector",
        path:     "myPath",
        rules: {
            domToModel: {
                "": {
                    transform: {
                        type: "fluid.transforms.stringToNumber",
                        inputPath: ""
                    }
                }
            },
            modelToDom: {
                "": {
                    transform: {
                        type: "fluid.transforms.numberToString",
                        inputPath: ""
                    }
                }
            }
        }
    }
}

In the above example:

1. A model change to the myPath variable will be transformed from a number to a string before the DOM element is updated.
2. A form element change will be transformed to a number before it is applied to the model.

If you do not supply any rules, be aware that non-string values will be converted to strings using their toString method. For objects, this results in the form values being set to the literal string [Object object].

Example 2: Using "long notation" to handle a single checkbox.

By default, checkboxes are treated as being part of an implicit group, and their values are all handled as strings. If no value attribute is specified for a checkbox, it's value is the literal string "on". If you want to provide a checkbox that will toggle a model variable between true and false, you can use additional transforms provided by this package, as illustrated in the following snippet:

    bindings: {
        myCheckBox: {
            selector: "myCheckBoxSelected",
            path:     "myModelVariable",
            rules: {
                domToModel: {
                    "": {
                        transform: {
                            type: "fluid.binder.transforms.checkToBoolean",
                            inputPath: ""
                        }
                    }
                },
                modelToDom: {
                    "": {
                        transform: {
                            type: "fluid.binder.transforms.booleanToCheck",
                            inputPath: ""
                        }
                    }
                }
            }
        }
    }

Note that the fluid.binder.transforms.checkToBoolean transform only checks the first value, so you can also use the above transformation rules in cases in which you want all of the checkboxes matching a selector to be checked if any of the individual checkboxes is selected.

Short notation

The "short form" uses the selector as the key, and the path as a string value (as in the second example above).

bindings: {
    "<selector2>": "<path2>"
}

Combining the two notations

You can use both forms together, as in:

bindings: {
    "<key>": {
        selector: "<selector1>",
        path:     "<path1>"
    },
    "<selector2>": "<path2>"
}

Static Functions

fluid.binder.applyBinding(component)

• component {Object} - A fluid viewComponent with both selectors and bindings options defined (see above).
• Returns: Nothing.

You must explicitly invoke this function to create bindings. Generally you wil do this from a listener definition. For example, if all required markup already exists on startup, you can simply bind to the "onCreate" event, as in:

listeners: {
    "onCreate.applyBindings": {
        "funcName": "fluid.binder.applyBinding",
        "args":     "{that}"
    }
}

The fluid.binder.bindOnCreate grade included with this package will do this for you.

Bindings and dynamic markup

If your component generates or regenerates markup, you will need to call fluid.binder.applyBinding(component) whenever it changes. The fluid.binder.bindOnDomChange grade included in this package will reapply the bindings whenever an onDomChange event is fired.

Tests

To run the tests in this package, run npm test. In addition to the normal test output, a test coverage report will be saved to reports/index.html.

If you want to debug the tests in a browser, you will need to somehow host the root directory, for example, using a command like python -m SimpleHTTPServer 7291. You would then open http://localhost:7291/tests/static/all-tests.html in your browser.