(Quick Reference)

8.3.4 Iterative Tags

Version: 3.2.4

8.3.4 Iterative Tags

Iterative tags are easy too, since you can invoke the body multiple times:

def repeat = { attrs, body ->
    attrs.times?.toInteger()?.times { num ->
        out << body(num)
    }
}

In this example we check for a times attribute and if it exists convert it to a number, then use Groovy’s times method to iterate the specified number of times:

<g:repeat times="3">
<p>Repeat this 3 times! Current repeat = ${it}</p>
</g:repeat>

Notice how in this example we use the implicit it variable to refer to the current number. This works because when we invoked the body we passed in the current value inside the iteration:

out << body(num)

That value is then passed as the default variable it to the tag. However, if you have nested tags this can lead to conflicts, so you should instead name the variables that the body uses:

def repeat = { attrs, body ->
    def var = attrs.var ?: "num"
    attrs.times?.toInteger()?.times { num ->
        out << body((var):num)
    }
}

Here we check if there is a var attribute and if there is use that as the name to pass into the body invocation on this line:

out << body((var):num)
Take notice to the usage of the parenthesis around the variable name. If you omit these Groovy assumes you are using a String key and not referring to the variable itself.

Now we can change the usage of the tag as follows:

<g:repeat times="3" var="j">
<p>Repeat this 3 times! Current repeat = ${j}</p>
</g:repeat>

Notice how we use the var attribute to define the name of the variable j and then we are able to reference that variable within the body of the tag.