switch(true) with dynamic cases in coldfusion?

Question

To avoid nested if-statements and to improve readability, I wanted to create a switch(true){ ... } statement in Coldfusion. I used this often in php, but when I try this in Coldfusion, I get the following error at initialization:

Template error

This expression must have a constant value.

This happens when a switch case uses a variable in its condition, like:

//this example throws the error
switch(true){
    case foo == 1:
        writeOutput('foo is 1');
    break;
}

Using a switch(true){ ... } statement with constant values (as the error explains) does work:

//this example doesn't throw the error
switch(true){
    case 1 == 1:
        writeOutput('1 is 1');
    break;
}

Is there any way to get the first statement to work in Coldfusion? Maybe with an evaluation of the variable or some trick, or is this a definite no go in Coldfusion?

Answer 1

In short: no. The case value needs to be something that can be compiled to a constant value. 1==1 can be, as it's just true. foo == 1 cannot be, as foo is only available at runtime.

basically what you're describing is an if / else if / else construct anyhow, so just use one of those.

Answer 2

As Adam and Leigh pointed out, the case values need to be some constant. I'm not sure what your actual use case is but you can do something like this:

switch(foo){
    case 1:
        writeOutput('foo is 1');
    break;
    case 2:
        writeOutput('foo is 2');
    break;
    case 3:
        writeOutput('foo is 3');
    break;
    case 4:
    case 5:
    case 6:
        writeOutput('foo is 4 or 5 or 6');
    break;
    default: 
        writeOutput("I do not have a case to handle this value: #foo#");
}