getIndex

int[] attrs { a, b, c }

obtainStyledAttrubites

TypedArray

SparseIntArray

attrs.indices

// get values specifying default ones for absent attributes
ta = obtain([a, b, c])
this.a = ta.get*(0, default);
this.b = ta.get*(1, default);
this.c = ta.get*(2, default);

// get values only for present attributes
for (i in 0..ta.indexCount) {
    idx = ta.getIndex(i)
    when (idx) {
        0 -> this.a = ta.get*(0, whatever)
        1 -> this.b = ta.get*(1, dontMind)
        2 -> this.c = ta.get*(2, unused)
    }
}