SVG.Pattern = SVG.invent({
  // Initialize node
  create: 'pattern',

  // Inherit from
  inherit: SVG.Container,

  // Add class methods
  extend: {
    // Return the fill id
    url: function () {
      return 'url(#' + this.id() + ')'
    },
    // Update pattern by rebuilding
    update: function (block) {
      // remove content
      this.clear()

      // invoke passed block
      if (typeof block === 'function') {
        block.call(this, this)
      }

      return this
    },
    // Alias string convertion to fill
    toString: function () {
      return this.url()
    },
    // custom attr to handle transform
    attr: function (a, b, c) {
      if (a === 'transform') a = 'patternTransform'
      return SVG.Container.prototype.attr.call(this, a, b, c)
    }

  },

  // Add parent method
  construct: {
    // Create pattern element in defs
    pattern: function (width, height, block) {
      return this.defs().pattern(width, height, block)
    }
  }
})

SVG.extend(SVG.Defs, {
  // Define gradient
  pattern: function (width, height, block) {
    return this.put(new SVG.Pattern()).update(block).attr({
      x: 0,
      y: 0,
      width: width,
      height: height,
      patternUnits: 'userSpaceOnUse'
    })
  }

})