component {
    variables.privateVar = "";

    public void function Init(){

    }

    public void function testThis(struct myStruct = {}){

        if(structKeyExists(myStruct,"fruit")){
            myStruct.fruit = "banana";
        }
        else if(structKeyExists(myStruct,"animal")){
            myStruct.animal = "tiger";
        }
    }
}

//invocation
<cfscript>
    test = new Test();

    myStruct = {fruit = ""};
    test.testThis(myStruct);

    //myStruct.fruit = banana

    writedump(myStruct);

    myStruct = {animal = ""};
    test.testThis(myStruct);

    //myStruct.fruit = banana
    writedump(myStruct);
</cfscript>