get the value from a pointer to a float32 from inside a struct?

Question

I am pulling in some data from a db - and I have a pointer to a float32 - because if I use a pointer - then I am able to check if it is nil (which it quite often might be).

When it is not nil, I want to get the value - how do I dereference it so I can get the actual float32? I can't actually find a link for that anywhere! I know exactly what I want to do, and I just can't find the syntax in Go, which I am still very new to - all help appreciated.

I know how to dereference the pointer if it is a straight float32...

but if I have the following struct...

type MyAwesomeType struct{
    Value *float32
}

Then after I do :

if myAwesomeType.Value == nil{
    // Handle the error later, I don't care about this yet...
} else{
    /* What do I do here? Normally if it were a straight float32
     * pointer, you might just do &ptr or whatever, but I am so
     * confused about how to get this out of my struct...
    */
}

Answer 1

The Go Programming Language Specification

Address operators

For an operand x of pointer type *T, the pointer indirection *x denotes the variable of type T pointed to by x. If x is nil, an attempt to evaluate *x will cause a run-time panic.

---

Use the * operator. For example,

package main

import "fmt"

type MyAwesomeType struct {
    Value *float32
}

func main() {
    pi := float32(3.14159)
    myAwesomeType := MyAwesomeType{Value: &pi}

    if myAwesomeType.Value == nil {
        // Handle the error
    } else {
        value := *myAwesomeType.Value
        fmt.Println(value)
    }
}

Playground: https://play.golang.org/p/8URumKoVl_t

Output:

3.14159

---

Since you are new to Go, take A Tour of Go . The tour explains many things, including pointers.

Pointers

Go has pointers. A pointer holds the memory address of a value.

The type *T is a pointer to a T value. Its zero value is nil .

 var p *int 

The & operator generates a pointer to its operand.

 i := 42 p = &i 

The * operator denotes the pointer's underlying value.

 fmt.Println(*p) // read i through the pointer p *p = 21 // set i through the pointer p 

This is known as "dereferencing" or "indirecting".

Unlike C, Go has no pointer arithmetic.