How Can I Access the Last Element of a Go Slice in a Template Without Custom Functions?

Retrieving the Last Element of a Slice in a Go Template

Question:

In a Go template, it's possible to get the size of a slice using len .Things and index it using index .Things 4. However, trying to index the last element using index .Things $size gives an error because indexing is zero-based. Is there an arithmetic solution without resorting to custom function definitions?

Answer:

While Go templates don't offer arithmetic operations natively, you can extend their functionality using a FuncMap. Here's how to add an "add" function:

t := template.Must(template.New("").Funcs(template.FuncMap{
    "add": func(a, b int) int { return a + b },
}).Parse(theTemplate)

This function takes two integers and returns their sum. In the template, it can be used as follows:

{{index .Things (add $size -1)}}

This will return the element at index $size - 1, effectively getting the last element of the slice.

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