How to initialize a bundle

bundle-init-code-frag

class MyBundle extends Bundle {
  val x = Bool()
  val y = UInt(8.W)
  val z = Bool()
}

object MyBundle {
  /**
    * initialize x and y but not z,
    * @return
    */
  def init1: MyBundle = {
    val wire = Wire(new MyBundle)
    wire.x := true.B()
    wire.y := 7.U
    wire
  }

  /**
    * This init takes an existing bundle to preserver unspecified values, in this case wire.x
    * @param current
    * @return
    */
  def init2(current: MyBundle): MyBundle = {
    val wire = Wire(new MyBundle)
    wire := current
    wire.y := 5.U
    wire.z := false.B
    wire
  }
}

class UseMyBundle extends Module {
  val io = IO(new Bundle{
    val something = Input(Bool())
    val outa = Output(new MyBundle)
    val outb = Output(new MyBundle)
  })

  // Use Case #1
  val reg_a = RegInit(MyBundle.init1)

  // Use Case #2
  val reg_b = Reg(new MyBundle)

  when (io.something) {
    reg_b := MyBundle.init1
  }.otherwise {
    reg_b := MyBundle.init2(reg_b)
  }

  io.outa := reg_a
  io.outb := reg_b
}