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From Reynold Xin <r...@databricks.com>
Subject Re: Question on Spark code
Date Mon, 24 Jul 2017 03:50:02 GMT
This is a standard practice used for chaining, to support

a.setStepSize(..)
  .set setRegParam(...)


On Sun, Jul 23, 2017 at 8:47 PM, tao zhan <zhantao92@gmail.com> wrote:

> Thank you for replying.
> But I do not get it completely, why does the "this.type“” necessary?
> why could not it be like:
>
> def setStepSize(step: Double): Unit = {
>     require(step > 0,
>       s"Initial step size must be positive but got ${step}")
>     this.stepSize = step
> }
>
> On Mon, Jul 24, 2017 at 11:29 AM, M. Muvaffak ONUŞ <
> onus.muvaffak@gmail.com> wrote:
>
>> Doesn't it mean the return type will be type of "this" class. So, it
>> doesn't have to be this instance of the class but it has to be type of this
>> instance of the class. When you have a stack of inheritance and call that
>> function, it will return the same type with the level that you called it.
>>
>> On Sun, Jul 23, 2017 at 8:20 PM Reynold Xin <rxin@databricks.com> wrote:
>>
>>> It means the same object ("this") is returned.
>>>
>>> On Sun, Jul 23, 2017 at 8:16 PM, tao zhan <zhantao92@gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> I am new to scala and spark.
>>>> What does the "this.type" in set function for?
>>>>
>>>>
>>>> ​
>>>> https://github.com/apache/spark/blob/481f0792944d9a77f0fe8b5
>>>> e2596da1d600b9d0a/mllib/src/main/scala/org/apache/spark/
>>>> mllib/optimization/GradientDescent.scala#L48
>>>>
>>>> Thanks!
>>>>
>>>> Zhan
>>>>
>>>
>>>
>

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