thinkphp fetch passes parameters inside

I want to pass a parameter a=1, how to pass it in

<code> echo $content = $this->fetch("Need@Need:readBizProduceOrder");</code>

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I want to pass a parameter a=1, how to pass it in

<code> echo $content = $this->fetch("Need@Need:readBizProduceOrder");</code>

Use a in template?

<code>$this->assign("a", 1);
echo $content = $this->fetch("Need@Need:readBizProduceOrder");</code>

Is $this here a Controller, a View, or a Template?