|If () Then|
The If () Then block is a Control block and a C block. The block checks its boolean condition. If the condition is true, the blocks held inside it will run, and then the script involved will continue. If the condition is false, the code inside the block will be ignored and the script will move on (unlike in the If () Then, Else block). The condition is only checked once; if the condition turns to false while the script inside the block is running, it will keep running until it has finished.
Before Scratch 2.0, this block was named If ().
The most basic uncertainty in programming is checking conditions. This block is Scratch's main way of doing that; it is therefore used in nearly all projects. Some common uses include:
- Comparing values
if <(answer) = > then say [Correct!] end
- Checking if input is given
if <<mouse down?> and <(amount) = >> then stamp end
- Controlling objects
if <key [space v] pressed?> then broadcast [Jump v] end
- Making sure a list contains a specific item
if <[list v] contains > then stop [all v] end
- Main article: List of Block Workarounds
This block can be replicated with the following code:
if <. . .::grey> then . . . else //Leave empty. end
Another workaround is this:
. . . broadcast [if statement v] and wait . . . when I receive [if statement v] repeat until <. . .::grey> stop [this script v] end . . .
Some users are confused as to why a script does not work when using the block. One of the most common misconceptions about it is that it repeatedly checks for a condition, so some users do not understand why a script isn't working with only the if block. To make it repeatedly check a condition, it simply needs to be put in a forever loop or another kind of repetition.
|Note:||The repeat until and repeat blocks can also be used to make a condition repeat, but only for a finite amount of time.|