Go Template if value is set and is false-CodePudding

I am using Listmonk which utilizes Go Templates. I have a situation where a variable for user status (.Subscriber.Attribs.Pro) may exist (and if it does, it is true or false. I want to display a block of text only if the value exists.

The code I have works if the Pro attribute is set. However if it is not set, it will be processed as not '' which leads to a value of true.

{{ if not .Subscriber.Attribs.Pro }}
  You are not a Pro user!
{{ end }}

How do I have this code run only if the Pro attribute is explicitly set to false

CodePudding user response：

So basically you only want to display the text if .Subscriber.Attribs.Pro is supplied and is false. So do a comparison:

{{ if eq false .Subscriber.Attribs.Pro }}
    You are not a Pro user!
{{ end }}

We can test it like:

t := template.Must(template.New("").Parse("{{ if eq false .Pro }}You are not a Pro user!\n{{ end }}"))

fmt.Println("Doesn't exist:")
if err := t.Execute(os.Stdout, nil); err != nil {
    panic(err)
}

fmt.Println("Pro is false:")
m := map[string]interface{}{
    "Pro": false,
}
if err := t.Execute(os.Stdout, m); err != nil {
    panic(err)
}

fmt.Println("Pro is true:")
m["Pro"] = true
if err := t.Execute(os.Stdout, m); err != nil {
    panic(err)
}

Output will be (try it on the Go Playground):

Doesn't exist:
Pro is false:
You are not a Pro user!
Pro is true:

As you can see, the {{if}} block is only executed when Pro is explicitly set to false.

CodePudding user response：

Use the included Sprig hasKey function:

{{if hasKey .Subscriber.Attribs "Pro"}}
    {{ if not .Subscriber.Attribs.Pro }}
        You are not a Pro user!
     {{ end }}
{{ end }}