How do you use a switch statement in GML?

Answer 1

Switch Statements are used to generate different outputs of code based on the value of an expression. Switch Statements work as follows:
{
randomNumber = floor(random(3))+1;
switch(randomNumber) {
case 1: { } break;
case 2: { } break;
case 3: { } break;
default: { } break;
}
}

This may seem confusing if you are new to GML, so I will give an in-depth explanation. The first line sets the variable randomNumber to a random number between 0 and 2, and adds it by 1 to make it a random number from 1-3. So far the only thing that has gone on in the code is to set a variable to either 1, 2, or 3. This is where the switch statement comes in.
switch(randomNumber) {
case 1: { } break;
case 2: { } break;
case 3: { } break;
default: { } break;
}
this is the actual switch statement. You may be wondering what the case statements are for. case statements are always written inside switch statements and do nothing anywhere else. case statements activate when the expression in the switch statement is the same as the value that they are assigned to. Take a look at this switch statement:
{
rand = floor(random(3));
switch(rand) {
case 0: {
show_message("The Random Value Was 0");
} break;
case 1: {
show_message("The Random Value Was 1");
} break;
case 2: {
show_message("The Random Value Was 2");
} break;
}
}

When the values assigned to the case statements are equal to the expression in the switch statement, the case statement will run the code contained in it's brackets. break statements order the switch statement to abort. The reason that you need break statements inside a switch statement is because it keeps the other cases from activating as well. (When one case statement activates, the others do as well.)
A final briefing on switch statements is that they are not limited to variables. Take a look at this switch statement.
{
switch(obj_block.x > x) {
case true: {
show_message("The Block Is Ahead Of You.");
} break;
case false: {
show_message("You Are Ahead Of The Block.");
} break;
}
}
This switch statement returns a true or false value, and the case statements operate accordingly.