Invokers

The public and implementation functions on your component ("methods", in OO terminology) are defined by configuration representing invokers.

Invokers can bind free functions, IoC resolved functions, and this based functions to the component, and to the context of the component. Invokers allow the signature received in the bound function to differ from the signature sent by the caller. As well as allowing the traditional OO facility for shifting the that argument representing the component itself in and out of the argument list, this also allows for much more powerful reuse of existing functions where signature elements can be sourced freely from around the component tree and within the original argument list.

Types of Invokers

Standard invoker binding to a function using funcName, func

An invoker can specified with either the funcName property to reference a free function by its global name (e.g. fluid.copy, fluid.log, etc.) or the func property to reference an existing function (perhaps another invoker) from elsewhere in the component tree.

An invoker record in context

The following skeleton example defines an invoker named invokerName attached to a component of type component.name. When a component of the type is instantiated, for example with a line such as var that = component.name();, the invoker will then be available as a function directly attached to the instance, callable under the name invokerName - e.g. as that.invokerName(...args...)

fluid.defaults("component.name", {
    // ...
    invokers: {
        invokerName: {
            funcName: "my.namespaced.function",
            args: [] // Array of arguments
        }
        // ...
    }
    // ...
});

Example:

The following example defines a component of type xyz.widget, with two invokers named addTwo and subtractTwo - the former binds onto a free function named xyz.widget.add, the latter binds onto another invoker elsewhere in the tree, which is not shown. Note that there is no necessary relationship between the name of a component and the name of a free function which is bound to it. If there is a close relationship between the purpose of a function and a related component, it is a helpful convention to prefix its name with the component name, as here - however, any free function may be bound via its global name to any component.

fluid.defaults("xyz.widget", {
    // ...
    invokers: {
        addTwo: {
            funcName: "xyz.widget.add",
            args: [2, "{arguments}.0"]
        },
        subtractTwo: {
            func: "{parent}.subtract",
            args: ["{arguments}.0", 2]
        }
    }
    // ...
});

xyz.widget.add = function (a, b) {return a + b;};

Compact format for invokers

Alternatively, invokers can be specified in a compact single line format. However, arguments specified in the invoker can only be strings or IoC References. Strings which can be converted into Numbers or Booleans will be so converted before being interpreted.

fluid.defaults("component.name", {
    // ...
    invokers: {
        invokerName: "<fully namespaced string name of function>(<comma-separated ioc references>)"
        // ...
    }
    // ...
});

Example:

fluid.defaults("xyz.widget", {
    // ...
    invokers: {
        addVal: "xyz.widget.add({that}.staticVal, {arguments}.0)",
        subtractVal: "{parent}.subtract({arguments}.0, {that}.staticVal)"
    }
    // ...
});

xyz.widget.add = function (a, b) {return a + b;};

Example:

fluid.defaults("fluid.uploader.fileQueue", {
    // ...
    invokers: {
        start: {
            funcName: "fluid.uploader.fileQueue.start",
            args: "{that}"
        },
        startFile: {
            funcName: "fluid.uploader.fileQueue.startFile",
            args: "{that}.currentBatch"
        }
        //...
    }
    //...
});

Invoker triggering a model change to some component's model

If the invoker's record contains the field changePath (rather than the standard func/funcName) this is recognised as a special type of invoker triggering a change to a particular component's model via its ChangeApplier. This type of record is documented in its own section with the ChangeApplier API. The compact syntax may not be used with this variety of record.

"this"-ist invoker binding to a OO-style JavaScript function referencing "this"

Specifying an invoker with a "this" property allows the invocation of functions whose body makes a reference to the special JavaScript value "this". These are generally functions external to the Infusion framework such as console.log, since it is a Fluid community standard to write "that"-ist functions whose execution is independent of the calling context. These can be any functions, but will most often be used for jQuery methods. See Declarative this-ism in IoC for more details. Note that the string this must always be quoted when appearing as a key as it is a JavaScript keyword.

Format

fluid.defaults("component.name", {
    // ...
    invokers: {
        invokerName: {
            "this": "console", // reference to an object
            method: "log", // string name of method on the this-ist object
            args: ["Hello, world."] // array of arguments
        }
    }
    // ...
});

Example:

fluid.defaults("xyz.widget", {
    // ...
    invokers: {
        setAriaLabel: {
            "this": "{that}.dom.elm",
            method: "attr",
            args: ["aria-label", "{arguments}.0"]
        }
    }
    // ...
});

Example:

fluid.defaults("fluid.uploader.html5Strategy.browseButtonView", {
    // ...
    invokers: {
        // ...
        disable: {
            "this": "{that}.dom.fileInputs",
            method: "prop",
            args: ["disabled", true]
        }
        // ...
    }
    // ...
});

Compact format

"this"-ist invokers have no equivalent compact syntax.