Loops

Loops let you repeat sections of your code. They’re a great shortcut — without them, you might have to connect the same blocks over and over again! Blockly has three different types of loops: 

• For loops will repeat the code inside them for the number of times you choose. There are two blocks that do this!
• While loops will repeat the code inside them while a certain condition that you set is true.
• Until loops will repeat the code inside them until a certain condition that you set is true.

For loops repeat the code that’s inside them for the number of times that you choose. Once that code has been repeated for that amount of time, your program will exit out of the loop and move on to the next block. 

Like we said in the first step, there are two for loop blocks in Blockly! One is the repeat for _ times block. To change the number in that block, you can just type in a new value. If you want to use a mathematical operation, equation, or variable, you can drag blocks from the math, logic, or variables menus to that gray area within the loop block.

The other for loop block is a little more complicated and looks more like what you would see in text-based coding. With this block, you would name a variable, and then you would set it to start at one number and go up to another. You can also set how much you want the value to increase by.

Ready to try for loops out? Program your CoDrone to look like it’s flying up a flight of stairs! The catch: since there are two different for loop blocks, you will need to write two different programs to try them out. Your CoDrone should keep moving forward and up. The programs might look different to you, but what happens when you run them?

While loops repeat the code that’s inside them while the condition that you set is true. Each time the program runs through the while loop, it checks to see if the condition is true. If it is not, your program will exit the loop.

You had your drone fly in a shape in the variables lesson, but now you can try it with a loop! Set your variable to 0, and then have it increase by 1 every time in the while loop. While your variable is less than or equal to 4, program your CoDrone to fly forward and then turn left (or vice versa). 

Wondering why you’re starting at 0? Humans begin counting at 1, but computers begin counting at 0!

You can program a while loop to run like a forever loop, which will repeat the code inside of it forever! All you need to do is set the condition to “While code is running”, and then make sure you have an emergency stop (as you always should!). You can also see what happens when you set the condition to false just by selecting that option from the drop-down menu. Try both loops with your CoDrone’s eye LEDs!

You may notice that the colors are switching very quickly. Add some Wait blocks from the timing section in between switching colors.

Until loops are a lot like while loops, except they’ll run the code inside the block until the condition is true. Each time the program runs through the while loop, it checks to see if the condition is true. If it is, the program will exit the loop, but after it finishes running that block of code one last time.

Set your variable to 0, and then have it increase by 1 every time in the while loop. Program your drone so that until your variable gets to 8, it will turn 1 second to either the left or right.

Challenge: Disco Drone 

Program your drone to turn like a disco ball with its eye and arm LEDs changing color!

Rules: 

• You must use at least one loop in your program. 
• Both the eyes and arms must change colors at least once.
• Don’t forget a kill switch!