Welcome to C# 102 for Space Engineers: Loops, Strings, and Other Things!

This guide assumes you have read C# 101 for Space Engineers. If you have not read this, some of this may not make sense.

We will be discussing more advanced concepts in C#, but not anything overly advanced: Loops, Strings, Inheritance, escape keywords, and ref.

Thank you to Shimonu of the Keen forums who assisted in verifying the functionality of the where() loop!

for loop:

The for loop is one of the more frequent loops you will encounter. The syntax is rather simple:

for(variable declaration; logical comparison; variable iterator){}

So what does this all mean?

Variable declaration – you may have noticed most of the time people put “int i = 0” here. This isn’t required—you can have any variable declared, even ones that have already been created. For instance, if I have a variable named “counter” initialized earlier than the loop:


This will work just the same. I can also assign a value during the declaration, as well—so if I wanted to set counter to 0, I can just use “counter = 0” during the declaration.

Logical comparison

This is usually something looked at to determine when the for loop is to end. Most of the time you’ll see something like, “i < blocks.Count” in the middle there. This is because we are going to make sure that “i” stays less than how many blocks are in the list of blocks. You can use anything you want, really, though to prevent an infinite loop (which the devs have explicitly stated won’t work) you should make sure the comparison is something that the loop can end. You CAN make an infinite loop (theoretically) if you terminate the loop using a keyword like “break” when you are checking for something inside the loop, though usually people will use the “while” loop that we will discuss later. A non-traditional for loop condition would be:

Recursion is a type of loop, though it is a bit more advanced than simply using a for, while, do-while, or foreach loop. How does recursion work? Through methods.



To recurse, you must call a method from itself. You should only recurse when you have a clear exit condition. If you do not, your code will not execute due to an infinite loop. If you aren’t sure why you should recurse in a particular situation, stick to normal loops. Basically, the best way to tell if you should use recursion is because you can’t figure out how to loop something iteratively. Recursion example (remember, this isn’t best practice—just a forced example demonstrating how it works.):




So, what happens here?

AddTwoNumbers(3,2) – k = 5. 5 < 10, so

AddTwoNumbers(5,2). – k = 7. 7 < 10 so

AddTwoNumbers(7,2). – k = 9. 9 < 10 so

AddTwoNumbers(9,2) – k = 11. 11 is not less than 10, so return 11.

Beacon is renamed to “11”

So, was that easier than for(int i = 3; i < 10; i) { i+=2;}?

No. Definitely not. Usually recursion is used for much more advanced things than adding two numbers. Also, notice that we had an if() statement in the method. This is because without it, it would recurse forever and the script will fail due to complexity.

Strings are very important. People use them every day, in every program. They also use them in Space Engineers all the time. So working with strings is kinda something all you SE scripter people want to know how to do.



So, first thing’s first: How to make a new line.


So, that looks simple, except for those confusing bits in the middle of the line? WTF is with the \n\r thing? Well, basically, in computer-speak, \n\r means “NEW LINE, CARRIAGE RETURN.” Ever wonder why some keyboards say “return” or people say “hit return” instead of the “ENTER” key on your keyboard? Well, it is called “return” because it is short for “Carriage Return.” Think of it as a throwback to typewriters. In a typewriter, a CR command would return the carriage to the beginning of the line. Clever, hm? New line should be self-explanatory.



We’ve already covered this briefly in 101, but here’s how you add a bunch of different things to a string:


So that will make s be “This is an example string that has 0 added to the back of it.”



Ok, what about case management? As I’ve mentioned before, strings are case-sensitive. That means comparing two strings that aren’t EXACTLY alike will return false: “Hi” == “hi” returns false. How do we fix something like this? Well, we can use ToUpper() and ToLower():


What does this do? Well, ToUpper() looks at your string and makes it ALL CAPITAL LETTERS. So if you type in a long string, like “THIS IS A LONG STRING THAT I WANT TO COMPARE.” And you have a variable that contains “This is a long string that I want to compare.”, ToUpper() will make the strings match. Alternatevely, you can use ToLower(), which does the opposite. Preference, really.



Another useful method is String.Contains(). This compares the thing inside the parenthesis with the string, returning true if it found that substring:


This would name a beacon:

True!

then

False!

Ok, what about the backslash and quotation mark characters? How do I put those in the strings? With the escape (\) character:
This would name the beacon: "I want a " here and a \ here."

Finally, I'd like to talk about String.Format(). This is an awesome string function- it lets you insert variables right into the middle of your string without all those pesky + in the middle!
The beacon would be named: "This is an example, where I insert the values "BLAH!" and "0" into the string."

There are a LOT of string functions, more than I want to talk about here. If you want to know what else you can do with strings, check out Microsoft Developer Network (Your Source for official C# Documentation!). Please note that MSDN is for C# in general, NOT Space Engineers. Because of this Your Mileage May Vary when using this documentation for coding in Space Engineers.

Strings: http://msdn.microsoft.com/en-us/library/system.string(v=vs.110).aspx

Wow, C# will give you money!? No. Sorry. Inheritance works a lot like that concept, only requires nothing to die and you only really inherit not having to write a lot of code again.



Ok, so what is inheritance? Well, we spoke about making a class in 101. Sometimes you have a class that is related to something else. So, for instance, a block is related to a light, because a light IS a block. Well, let’s assume a block has an ID code and a damage value:


Well, lights have that, too, but let’s say they also have an “On” value:


Well, I don’t want to have to also define ID and damage to the light, because I’m lazy. (Laziness is a good trait in programmers—you’ll work less hard to achieve the same result). So we’ll inherit:


So what did I do here? Well, : means “Inherit from” when you define your class. So this says “Light inherits from Block.” When we make the initializer, we say that light requires an id value, a damage value, and an on/off state value. Instead of having to define all of that, we just tell it to initialize it with the values i and d passed to the base class (aka, block).



If you have a method in the base class, say, “SetID()” and you want to use it in the class, you would simply put:


Which tells the code “check the class I’m inheriting from for a method called “SetID” and then run it with the parameter “123”.

You’ll notice that you can do a lot of the same stuff with the same block interfaces: this is because the blocks all inherit from other types of blocks, creating a hierarchy. Makes for a lot less coding.

There are two keywords I want to talk about. These are “escape keywords.” I call them that because they have the power to escape the current loop or method you are in.



return – If you call this, it returns a value immediately and terminates the method you are in. If your method has a type other than void, you must return a type (return 0) with it. If it has void, you can simply say “return;” to have it terminate the method.



break – Stop processing the loop. Do not pass go, do not collect $200.


This would name the beacon “0” and immediately stop.



Why are these important? Well, sometimes you reach a condition and you want it to completely stop what it is doing when it reaches that condition. Return and break force what the script is doing to come to a complete halt right at that line. Return should only be at the end of a method or inside of an if() or switch() statement. If you do this:


The line “int k = i+j;” would never execute.

Ok, so there is one final keyword I want to talk about: ref. Ref is used to pass a variable by reference. See what they did there? So, let’s take a look at ref:


The beacon would be named 10.

This allows you to pass a variable into a method without having to find ways to return it. Ref is mainly useful if you have a whole host of parameters you all need processed at once and need them all to retain their changes when done. In general, this should be done with multiple methods rather than ref, but sometimes ref is a necessary thing.

out:
This keyword works like ref, only doesn't require the variable you are passing in to be initialized ahead of time:
This would set the beacon to 10, also.

Thanks to pipakin of the Keen forums for reminding me to put out in this guide.

Recursion – The best way to define recursion is to use recursion.

Iteration – a process which will eventually lead to a result. If we add 1 to i until it becomes 10, each value of i is an iteration of i. Loops are iterative— their function is to repeat a process until you reach a specific result, then end the loop.