How to clear the bound value of a lookup PCF

[Polmon]

I've created my own Lookup PCF for my model driven app; it's quite a complicated control that gives the user a load of different options for populating the control, and the control works perfectly for setting a value however I cannot find a way to clear the value once it has been set (the equivalent of clicking the X next to the value in a normal OOB lookup control).

Looking at the sample PCF for a lookup (LookupSimpleControl), it passes in a function to set the value of the local property, which is then returned by the getOutputs(), using the value {} as ComponentFramework.LookupValue, as detailed below:

Global Variables used in the sample control:

// Used to store necessary data for a single lookup entity selected during runtime
private _selectedItem1: ComponentFramework.LookupValue;
private _selectedItem2: ComponentFramework.LookupValue;

// Used to track which lookup property is being updated
private _updateSelected1 = false;

Where the event is bound and the variable value is set

lookupObjectsButton1.onclick = this.performLookupObjects.bind(this, this._entityType1, this._defaultViewId1, (value, update = true) => {
this._selectedItem1 = value;
this._updateSelected1 = update;
});

The method setting (and clearing) the value:

private performLookupObjects(entityType: string, viewId: string, setSelected: (value: ComponentFramework.LookupValue, update?: boolean) => void): void {
// Used cached values from lookup parameter to set options for lookupObjects API
const lookupOptions = {
defaultEntityType: entityType,
defaultViewId: viewId,
allowMultiSelect: false,
entityTypes: [entityType],
viewIds: [viewId]
};

this._context.utils.lookupObjects(lookupOptions).then((success) => {
if (success && success.length > 0) {
// Cache the necessary information for the newly selected entity lookup
const selectedReference = success[0];

const selectedLookupValue: ComponentFramework.LookupValue = {
id: selectedReference.id,
name: selectedReference.name,
entityType: selectedReference.entityType
};

// Update the primary or secondary lookup property
setSelected(selectedLookupValue);

// Trigger a control update
this._notifyOutputChanged();
} else {
setSelected({} as ComponentFramework.LookupValue);
}
}, (error) => {
console.log(error);
});
}

getOutputs method:

public getOutputs(): IOutputs {
// Send the updated selected lookup item back to the ComponentFramework, based on the currently selected item
return this._updateSelected1 ? { controlValue: [this._selectedItem1] } : { controlValue1: [this._selectedItem2] };
}

How the properties are registered in the ControlManifest.Input.xml file:

<property name="controlValue" display-name-key="controlValue_Display_Key" description-key="controlValue_Desc_Key" of-type="Lookup.Simple" usage="bound" required="true" />
<property name="controlValue1" display-name-key="controlValue_Display_Key1" description-key="controlValue_Desc_Key1" of-type="Lookup.Simple" usage="bound" required="true" />

This is essentially the same way my control works, except I'm not using the lookupObjects method, and have a button to clear the value.

My global variable:

private _selectedItem: ComponentFramework.LookupValue;

My event binding:

this._buttonClearField.onclick = this.onClearClick.bind(this, (value) => {
this._selectedItem = value;
});

My click event which clears the value:

private async onClearClick(setSelected: (value: ComponentFramework.LookupValue) => void) {
// Clear the lookup property
setSelected({} as ComponentFramework.LookupValue);
}

My getOutputs method:

public getOutputs(): IOutputs
{
return { boundField: [this._selectedItem] };
}

My control property:

<property name="boundField" display-name-key="Bound Field" description-key="The field the control is bound to" of-type="Lookup.Simple" usage="bound" required="true" />

This looks the same to me. After the clear event runs, the _selectedItem property is cleared, but the context.parameters.boundField value doesn't seem to get updated, and when the record on the form is saved, the field value isn't cleared. I've tried calling notifyOutputChanged, manually clearing the value from context.parameters.boundField, but the field value just doesn't get cleared.

I haven't managed to get the sample PCF working yet to see if that actually works, that's my next step (I'm just setting up and env and app I can use for that.

Is there anything in the above that looks wrong? Has anyone else encountered this issue, or managed to clear a bound lookup value from their PCF? Please help, this has been driving me nuts for a few weeks now.

[Polmon]

I've had a chance to try out the sample control now, and the cancel function (where it uses the setSelected function to return {} as ComponentFramework.LookupValue) doesn't do anything unfortunately, it just cancels the lookup dialog without returning a value to update the bound property. Still no idea how to clear the bound property of a lookup PCF unfortunately.

[DianaBirkelbach]

Hi @Polmon , 

try to change the getOutputs to something like this

public getOutputs(): IOutputs
{
return { boundField: this._selectedItem ? [this._selectedItem] : undefined };
}

Using the "return {}" will not change any property, you need to pass undefined in order to notify the framework that your value was changed/removed.

Of course you need to change the onClearClick to set the value on undefined

private async onClearClick(setSelected: (value: ComponentFramework.LookupValue) => void) {
// Clear the lookup property
setSelected(undefined);
}

Inside the "setSelected" you need to call the 

this._notifyOutputChanged()

Hope this helps!

[Polmon]

Hi Diana, I've just had a go at that; I can't use null as boundField is ComponentFramework.LookupValue[] | undefined, so I tried using undefined instead as follows:

public getOutputs(): IOutputs
{
return { boundField: this._selectedItem ? [this._selectedItem] : undefined};
}

Unfortunately, this didn't work, clearing the field doesn't show the form as unsaved and saving subsequently doesn't clear the field. I also tried using {} as ComponentFramework.LookupValue in getOutputs too as shown below, but that doesn't work either.

public getOutputs(): IOutputs
{
return { boundField: this._selectedItem ? [this._selectedItem] : {} as ComponentFramework.LookupValue};
}

I tried dropping notifyOutputChanged in to my clear button event too, but that didn't make a difference either.

Have you managed to get this working?

[DianaBirkelbach · Accepted solution]

Hi @Polmon , 

You're right, you need to set the value to undefined.
Of course you need to change the onClearClick, to set the value to undefined (not to {}).
The notifyOutputChanged need to be called too.

Can you please check with the debugger or logging that the value passed through getOutputs is undefined...
Yes, I've just checked, and I can clear the value of a lookup that way.

I've changed the first answer with this details, just to have them all together.

Hope this helps!

[Polmon]

Yes! That was it. I needed to change the declaration of the value everywhere it was used, but it's working now.

For the benefit of anyone else, I'll detail below the working setup.

The variable that's returned:

private _selectedItem: ComponentFramework.LookupValue | undefined;

The binding for the button click event (the _notifyOutputChanged reference is set to the parameter passed into the init function):

this._buttonClearField.onclick = this.onClearClick.bind(this, (value) => {
    this._selectedItem = value;
    this._notifyOutputChanged();
});

 The clear button click implementation: 

private async onClearClick(setSelected: (value: ComponentFramework.LookupValue | undefined) => void) {
    // Clear the lookup property
    setSelected(undefined);
}

In getOutputs, just pass back the value or undefined (I could probably just pass back _selectedItem here without the check):

public getOutputs(): IOutputs
{
    return { boundField: this._selectedItem ? [this._selectedItem] : undefined };
}

And that's it, the value is cleared on click now. Thank you @DianaBirkelbach!