How Can I Determine if a Struct Property Has Been Assigned a Value in Go?

Determining Property Assignment in Structs

Many scenarios in programming involve working with structures and their properties. One common question that arises is how to determine if a specific property within a structure has been assigned a value. This article will explore a solution to this problem.

In Go, structures are value types, which means that assigning a new value to a structure property creates a new copy of the structure. This behavior can complicate checking whether a property has been set.

As suggested by dyoo in the provided answer, one approach is to use nil values. If the property is a pointer, you can check if it is nil to determine if the property has been set. However, this approach is not applicable if the property is not a pointer.

Alternatively, you can compare the property value to a default value, such as an empty string. The following example demonstrates this approach:

package main

import "fmt"

type MyStruct struct {
    Property string
}

func main() {
    s1 := MyStruct{
        Property: "hey",
    }

    s2 := MyStruct{}

    if s1.Property != "" {
        fmt.Println("s1.Property has been set")
    }

    if s2.Property == "" {
        fmt.Println("s2.Property has not been set")
    }
}

In this example, if the Property field of s1 is not empty, the code prints that it has been set. Conversely, if the Property field of s2 is empty, the code prints that it has not been set.

This approach allows you to determine if a struct property has been assigned a value, regardless of whether the property is a pointer or not. By comparing the property value to a default value, you can effectively check for assignment.

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