Programmatic element (pre-)selection on datatable fails when using dataKey

[gdj1975]

I'm submitting

[ x ] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Plunkr Case (Bug Reports)
Please fork the plunkr below and create a case demonstrating your bug report. Issues without a plunkr have much less possibility to be reviewed.

http://plnkr.co/edit/UZiAHEmvc3IldUTHTNyH?p=preview

Current behavior
Setting a selected item on a datatable that uses a dataKey does not work in single selction mode. The selection object and the selection keys are not correctly initialized, when selection is a single object instead of an array.

Expected behavior
Setting the selected item as object in single selection mode should use the datakey property to check equality.

Minimal reproduction of the problem with instructions
http://plnkr.co/edit/UZiAHEmvc3IldUTHTNyH?p=preview

** Issue and Fix

primeng/src/app/components/datatable/datatable.ts

Lines 851 to 855 in d75ad83

	if(this._selection) {
	for(let data of this._selection) {
	this.selectionKeys[String(this.objectUtils.resolveFieldData(data, this.dataKey))] = 1;
	}
	}

        if(this._selection) {
            if (Array.isArray(this._selection)) {
                for(let data of this._selection) {
                    this.selectionKeys[String(this.objectUtils.resolveFieldData(data, this.dataKey))] = 1;
                }
            }
            else {
                this.selectionKeys[String(this.objectUtils.resolveFieldData(this._selection, this.dataKey))] = 1;
            }
        }

• PrimeNG version: 4.1.2

[hugograf]

I can confirm this error. The fix of "gdj1975" would fix this problem!

[cagataycivici]

Got it, thanks.