Promise attributes?

[kyasbal]

Asynchronous attributes typically hard to operate them. We need feature to handle asynchronous attributes easily.

Change behaviour of fetching attribute if the attribute converter returned Promise.

If an converter returned a Promise instance, Attribute#value should be resolved value.
For example, material is asynchronous attribute.

function convertMaterial(){
    return new Promise((resolve,reject)=>{
    // SOMETHING
    resolve(new Material(....));
    });
}

Before this feature

NodeInterface#getAttribute("material") => Promise<Material>;

After this feature

NodeInterface#getAttribute("material") => Material;

Several API changes

For changing this feature, we need define several APIs.

watch API

watch API also should be fired when the attribute was resolved.

watch("material",(mat:Material)=>{ // mat should be Material instance. not Promise.

});

if immediate flag is set, the watch function is fired after resolving current Promise.

isPending API

isPending provides information that specified attribute is waiting for Promise or not.

Component#isPending(attributeName:string):boolean;

NodeInterface#setAttribute, Component#setAttribute

These method should return Promise instance that is currently waiting for.

Before this feature

NodeInterface#setAttribute("material",something)=>void;

After this feature

NodeInterface#setAttribute("material",something)=>Promise<Material>;