AIML: Think/Set on button click

Question

How do I Think/Set a variable only when a button has been clicked. I have multiple buttons in a template and I want to set the value of the variable based on the button the user clicks on. I don't know how to do this without using multiple assignments of the variable with the Think/Set tag and the variable ends up being with the last value assignment.

<category>
        <pattern>quiz</pattern>
        <template>
         Which of these topics are most interesting to you?
            <button>
                <text>topic1</text>
                <postback>question 2</postback>
                <think><set name = "question1">1</set></think>
            </button>
            <button>
                <text>topic2</text>
                <postback>question 2</postback>
                <think><set name = "question1">2</set></think>
            </button>
            <button>
                <text>topic3</text>
                <postback>question 2</postback>
                <think><set name = "question1">3</set></think>
            </button>
            <button>
                <text>topic4</text>
                <postback>question 2</postback>
                <think><set name = "question1">4</set></think>
            </button>
            <button>
                <text>topic5</text>
                <postback>question 2</postback>
                <think><set name = "question1">5</set></think>
            </button>
        </template>
    </category>

Answer 1

As you have already seen, you can't set variables within button or reply tags. Instead, you should pass any values to the category itself via the postback, like this:

<category>
    <pattern>quiz</pattern>
    <template>
     Which of these topics are most interesting to you?
        <button>
            <text>topic1</text>
            <postback>question 2 1</postback>
        </button>
        <button>
            <text>topic2</text>
            <postback>question 2 2</postback>
        </button>
        <button>
            <text>topic3</text>
            <postback>question 2 3</postback>
        </button>
        <button>
            <text>topic4</text>
            <postback>question 2 4</postback>
        </button>
        <button>
            <text>topic5</text>
            <postback>question 2 5</postback>
        </button>
    </template>
</category>

<category>
    <pattern>question 2 *</pattern>
    <template>
        <think><set name="question1"><star/></set></think>
        You clicked on topic <get name="question1"/>.
    </template>
</category>