Corona SDK – scale object on touch event

utility.lua

function scaleObject(event, scale)
    assert(event, "event is missing")
    local object = event.target
    local scale = scale or 0.95

    if event.phase == "began" then
        object.xScale = scale
        object.yScale = scale
        object.isFocus = true
        display.getCurrentStage():setFocus(object)
    end

    if event.phase == "moved" then
        if event.x > object.contentBounds.xMax - 1
            or event.x < object.contentBounds.xMin + 1
            or event.y < object.contentBounds.yMin + 1
            or event.y > object.contentBounds.yMax - 1 then
                object.xScale = 1
                object.yScale = 1
                object.isFocus = false
        else
            if not object.isFocus then
                object.xScale = scale
                object.yScale = scale
                object.isFocus = true
            end
        end
    end

    if event.phase == "ended" then
        object.xScale = 1
        object.yScale = 1
        display.getCurrentStage():setFocus(nil)
    end

    if not object.isFocus then
        event.phase = nil
    end
end