Struct field names starting with a string

Question

I have a go struct and I need to work with one of the fields. However I am starting with a string. How do I case it to get the field itself.

package main
import "fmt"

func main() {

    type Point struct{
  x int
  y int
}

    pt := Point{x:2, y:3}
    a  := "x"
    fmt.Printf("%s", pt.a)
}

Since a = "x" I am expecting pt.x = 2. Here's the error message it prints out. I am definitely starting with a string so I can't just remove the quotation marks.

$ go run point.go
# command-line-arguments
./point.go:14: pt.a undefined (type Point has no field or method a)

Is this Point struct your actual use case? Are you able to explain a little more about where you are trying to do this? — user142162
– user142162, Commented Oct 25, 2015 at 14:31

Satyen Rai · Accepted Answer · 2015-10-26 15:11:39Z

3

If you need to access a field whose name is given as a string, you have no choice but to use reflection. Go ain't Python. :-)

This blog has a nice explanation.

Here is the reflect package documentation.

But note that reflection should usually be used as a last resort only. It removes the static type safety and is detrimental for performance.

What are you really looking for? There may be a way to address your requirements without using reflection. For example, if you don't need methods attached to your struct, you could use map[string]int.

answered Oct 26, 2015 at 15:11

Satyen Rai

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