Change vertices in box2d polygon

? Offline

hi, everybody.
i'm writing game, using qml & box2d. there's file containing box2d polygon and image:
@
import QtQuick 1.0
import Box2D 1.0

Body {
id: block
fixedRotation: false
sleepingAllowed: false
bodyType: Body.Static

property variant __x: []
property variant __y: []
property alias image: image.source

function setBlock(x,y)
{
    __x = x;
    __y = y;
    polygon.vertices = [
        Qt.point(__x[0],__y[0]),
        Qt.point(__x[1],__y[1]),
        Qt.point(__x[2],__y[2]),
        Qt.point(__x[3],__y[3]),
    ];
}

fixtures: Polygon {
    id: polygon
    anchors.fill: parent
    density: 0;
    friction: 10;
    restitution: 1;
    vertices: [
        Qt.point(__x[0],__y[0]),
        Qt.point(__x[1],__y[1]),
        Qt.point(__x[2],__y[2]),
        Qt.point(__x[3],__y[3]),
    ]
}

Image {
    id: image
    x: __x[2]
    y: __y[1]
    width: __x[0] - __x[2]
    height: __y[0] - __y[1]
    fillMode: Image.Tile
    source: "../../img/block_.png"
}

Behavior on x { SmoothedAnimation { velocity: 300 } }
Behavior on y { SmoothedAnimation { velocity: 300 } }

}
@

i create it dymanically from javascript like this:
@
var dynamicObject = block.createObject(world,{"__x": var_1,"__y":var_2});
@
If i try to change vertices, using setBlock() method polygon's coordinates stay the same, only image changes.
Does somebody know what to do?

? Offline

I've found that it's possible to recreate object with new vertices:
@
blockArray[i].destroy();
var block = Qt.createComponent("Block.qml");
if (block.status == Component.Ready) {
var dynamicObject = block.createObject(world,{"__x": x,"__y": y});
blockArray[i] = dynamicObject;
}
@
But it's not the solution of problem, it's just the way to make it work