How to Handle Conditional Rendering in Go HTML Templates with Else If?

Handling Conditional Rendering in Go HTML Templates

When rendering HTML templates in Go, it's often necessary to display content differently based on specific conditions. One common approach is to use nested if/elseif/else constructs. However, for cases with a large number of conditions, this can lead to cluttered code.

Consider the following Go struct:

const (
    paragraph_hypothesis = 1<<iota
    paragraph_attachment = 1<<iota
    paragraph_menu       = 1<<iota
)

type Paragraph struct {
    Type int // paragraph_hypothesis or paragraph_attachment or paragraph_menu
}

You wish to display paragraphs in a way that depends on their type. While it's possible to use nested if statements like this:

{{range .Paragraphs}}
    {{if .IsAttachment}}
        -- attachment presentation code  --
    {{else}}{{if .IsMenu}}
        -- menu --
    {{else}}
        -- default code --
    {{end}}{{end}}
{{end}}

this approach becomes unwieldy with more types, resulting in both cluttered Go code (with functions like IsSomething) and template code (with nested {{end}} statements).

Fortunately, there's a cleaner solution in Go templates: the else if construct. Using this, you can simplify the above template as follows:

{{range .Paragraphs}}
    {{if .IsAttachment}}
        -- attachment presentation code  --
    {{else if .IsMenu}}
        -- menu --
    {{else}}
        -- default code --
    {{end}}
{{end}}

By using else if, you can eliminate the need for multiple nested if statements, making your template code more concise and easy to follow.

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