Table of Contents

Control Flow

LunyScript has two types of blocks:

  • ActionBlock types execute/run something, typically changing state.
  • ConditionBlock types evaluate a logical expression for being either true or false.

We use them together to create logic via control flow blocks.

If().Then()

The simplemost control flow statement is the If().Then() pattern:

On.Ready(
    If(Object.IsVisible())
        .Then(Debug.Log("potentially visible"))
);

If().Then().ElseIf().Then()

Of course you can have multiple branches with ElseIf().Then():

On.Heartbeat(
    If(Rigidbody.Speed() < 10)
        .Then(Debug.Log("going slow"))
    .ElseIf(Rigidbody.Speed() < 20)
        .Then(Debug.Log("running"))
    .ElseIf(Rigidbody.Speed() < 30)
        .Then(Debug.Log("running fast"))
);

If().Then().ElseIf().Then().Else()

You can have a final Else() block which runs when no other branch is true:

On.Heartbeat(
    If(Rigidbody.Speed() < 10)
        .Then(Debug.Log("going slow"))
    .ElseIf(Rigidbody.Speed() < 20)
        .Then(Debug.Log("running"))
    .ElseIf(Rigidbody.Speed() < 30)
        .Then(Debug.Log("running fast"))
    .Else(Debug.Log("going really fast"))
);

While().Do()

You can execute blocks for as long as conditions are true with the While().Do() pattern:

On.Heartbeat(
    While(Rigidbody.Speed() < 10)
        .Do(Rigidbody.AddForce(LunyVector3.one))
);
Warning

It is trivial to create infinite loops with While(). Internally it is safeguarded against potential infinite loops, but the editor/build may remain frozen for several seconds. If it happens to you, give it some time. Unlike C# infinite loops it will unfreeze eventually. Note: The safeguard is inactive in RELEASE builds.

For().Do()

The For().Do() loop should also seem familiar, except it's simplified to a single numeric value:

On.Ready(
    For(10)
        .Do(Debug.Log("for loop iterating"))
);

This will log ten times. Note that internally this counts from 1 to 10, just like Lua.

If you need a custom step other than +1 you can specify the step as the second parameter:

On.Ready(
    For(10, 2)
        .Do(Debug.Log("for loop iterating"))
);

This will log five times because the increment step is 2 (default: 1).

For().Do() Backwards

Sometimes, you need to iterate backwards. You can do this by passing a negative step value:

On.Ready(
    For(10, -1)
        .Do(Debug.Log("for loop iterating"))
);

This will log ten times but will decrement from 10 to 1.

Tip

The loop counter value is useful to use in the actions the For() loop runs. It will be exposed in the future. In the meantime you can manually Inc() or Dec() a variable in the Do() block.

Loop With Variables

What good are loop expressions without variables? Of course you can use variables in For() and While() loops:

var enemyCount = Var.Define("enemyCount", 3);
var createEnemy = Object.Create("enemy").With("Assets/Prefabs/Enemy");

On.Enabled(
    For(enemyCount).Do(createEnemy),
    enemyCount.Add(3)
);

This will create three enemies the first time the object gets enabled. The next time it will create six, then nine, and so forth.

Logical Operators

The default combination of multiple conditions is an implicit AND where all conditions must be true for the check to pass:

On.Ready(
    If(c1, c2, c3) // all three must be true
        .Then(Debug.Log("check passed"))
);

But sometimes you may need to use other logical expressions ...

The C# expression c1 && (c2 || c3) is in plain english c1 AND (c2 OR c3). Its block equivalent is:

If(c1, OR(c2, c3)).Then(..)

The C# expression c1 || (c2 && c3) is in plain english c1 OR (c2 AND c3). Its block equivalent is:

If(OR(c1, AND(c2, c3))).Then(..)

The C# expression !(c1 || (c2 && c3)) is in plain english NOT (c1 OR (c2 AND c3)). Its block equivalent is:

If(NOT(OR(c1, AND(c2, c3)))).Then(..)

As usual, you can pull out those checks into C# variables to keep your blocks readable, and maintainable:

var check = NOT(OR(c1, AND(c2, c3)));

On.Ready(If(check).Then(Debug.Log("check passed")));
Warning

Every logical operator, every additional condition increases cognitive load! One condition is trivial. Two conditions easy. Three conditions take a moment. Add NOT, OR, AND in between and repeat the conditions several times, with variations? 😵‍💫🫨🤯

It's easy to create unmanageable messes with complex logical expressions! #1 Rule of Programming: KEEP IT SIMPLE, STUPID! 😊

Note

Other logical operators will be added later. I know some of you would love to do intricate logic puzzles. That's when you might need to XNOR the NAND out of conditions. 🤓

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