Derived property depending on other derived properties

[agentS]

Hi,

I am currently developing an application depending on a derived property to enable or disable a button. However, this derived property depends on an amount of other derived properties which depend on regular properties. For debugging purposes I added an output line in the top level property (the one relying on the derived ones) which shows the returned value and this is working as demanded. However, listening for changes does not work, although it works when I exchange the property depending on the derived properties with a property calculated when a regular property changes.

I hope the following source code supports my explanation:

props:
{
    a: [ "number" ],
    b: [ "number" ]
},
derived:
{
    isValid:
    {
        deps:
        [
            "isAValid",
            "isBValid"
        ],
        fn: function()
        {
            console.log((this.isAValid && this.isBValid)); // works fine
            return (this.isAValid && this.isBValid);
        }
    },
    isAValid:
    {
        deps: [ "a" ],
        fn: function()
        {
            var checkResult = ...;// validity check
            return checkResult;
        }
    },
    isBValid:
    {
        deps: [ "b" ],
        fn: function()
        {
            var checkResult = ...;// validity check
            return checkResult;
        }
    }
}
...
this.model.on("change:isValid", ...) // doesn't work
this.model.on("change:isAValid", ...) // works

[kamilogorek]

Add cache: false to your derived properties that has to be checked every time.

[agentS]

Thanks a lot, this works great!

Am 2015-11-12 um 12:12 schrieb Kamil Ogórek:

Add cache: false to your derived properties that has to be checked every time.

---

Reply to this email directly or view it on GitHub: https://github.com/AmpersandJS/ampersand-state/issues/216#issuecomment-156076715

[kamilogorek]

Glad I could help. Cheers!