How to Concatenate Strings Efficiently in Go Templates?

Efficiently Concatenating Strings in Templates

Question:

In Go templates, is there an efficient way to concatenate strings using operators like " "?

Examples Provided:

<code class="go">{{ $var := printf "%s%s" "x" "y" }}
{{ TestFunc $var }}  // Returns "xy"

{{ $var := "y" }}
{{ TestFunc "x" + $var }}  // Error: unexpected "+" in operand

{{ $var := "y" }}
{{ TestFunc "x" + {$var} }}  // Error: unexpected "+" in operand</code>

Answer:

Go templates do not support operators for string concatenation. Hence, the above examples will result in errors.

Solutions:

1. Use the printf Function:
   As demonstrated in the first example, you can use the printf function to concatenate strings. This method is efficient and flexible.

   <code class="go">{{ $var := printf "%s%s" "x" "y" }}
   {{ TestFunc $var }}  // Returns "xy"</code>

2. Combine Template Expressions:
   You can also combine multiple template expressions to achieve concatenation.

   <code class="go">{{ TestFunc (printf "%s%s" "x" "y") }}  // Returns "xy"</code>

3. Modify the TestFunc Argument Handling:
   If your use case always involves concatenating strings for the TestFunc argument, you can modify the function to handle concatenation internally.

   <code class="go">func TestFunc(strs ...string) string {
       return strings.Trim(strings.Join(strs, ""), " ")
   }
   
   {{ TestFunc "x"  $var }}  // Returns "xy"</code>

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