How to Modify a Simple Type\'s Value Using a Pointer Receiver in Go?

Modifying Value of a Simple Type through Pointer Receiver in Go

Modifying the value of a simple type through a pointer receiver method can be a common task in Go. However, understanding how pointers behave in this context is crucial.

In the provided example:

<br>type FooInt int</p>
<p>func (fi *FooInt) FromString(i string) {</p>
<pre class="brush:php;toolbar:false">num, _ := strconv.Atoi(i)
tmp := FooInt(num)
fi = &tmp

}

When a pointer is passed as a receiver, a copy of that pointer is created within the method. Any modifications made to the copy inside the method will not affect the original pointer.

In the code snippet, *fi is a copy of the fi pointer passed to the FromString method. When you assign &tmp to *fi, you are essentially changing the copy's value, not the original fi pointer.

To modify the original pointer's value, you need to either:

• Return the new pointer value:
  

  <br>  func (fi <em>FooInt) FromString(i string) </em>FooInt {</p>
  <pre class="brush:php;toolbar:false">  num, _ := strconv.Atoi(i)
    tmp := FooInt(num)
    return &tmp

  }
  

• Pass a non-nil pointer to the value you want to change:
  

  <br>  func (fi <em>FooInt) FromString(i string, p </em>*FooInt) {</p>
  <pre class="brush:php;toolbar:false">  num, _ := strconv.Atoi(i)
    tmp := FooInt(num)
    *p = &tmp

  }
  

• Ensure the receiver is not nil:
  

  <br>  func (fi *FooInt) FromString(i string) {</p>
  <pre class="brush:php;toolbar:false">  num, _ := strconv.Atoi(i)
    *fi = FooInt(num)

  }
  

By ensuring that the receiver is a valid pointer and modifying the pointed value inside the method, you can effectively modify the value of the original simple type through a pointer receiver.

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