View source for If () Then (block)

{{block
| name        = If () Then
| image       = If () then
| imagewidth  = 71
| category    = [[Control Blocks|Control]]
| type        = [[C Block|C]]
| sb          = yes
}}
The '''If () Then''' [[Blocks|block]] is a [[Control Blocks|Control block]] and a [[C Block|C block]]. The block checks its [[Boolean Block|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)|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 ().

== Example Uses ==
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

<scratchblocks>
if <(answer) = [5]> then
say [Correct!]
end
</scratchblocks>

* Checking if input is given

<scratchblocks>
if <<mouse down?> and <(amount) = [1]>> then
stamp
end
</scratchblocks>

* Controlling objects

<scratchblocks>
if <key [space v] pressed?> then
 broadcast [Jump v]
end
</scratchblocks>

== Workaround ==
{{main|List of Block Workarounds}}
This block can be replicated with the following code:

<scratchblocks>
if <. . .> then
. . .
else
//Leave empty.
end
</scratchblocks>

Another workaround is this:

<scratchblocks>
. . .
broadcast [if statement v] and wait
. . .

when I receive [if statement v]
repeat until <statement false::operators>
stop [this script v]
end
. . .
</scratchblocks>

== Common Issue ==
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,<ref>http://scratch.mit.edu/discuss/topic/14843/</ref><ref>http://scratch.mit.edu/discuss/topic/26823/?page=1#post-237085</ref> 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|forever loop]] or another kind of repetition.
{{note|The [[Repeat Until ()|repeat until]] and [[Repeat ()|repeat]] blocks can also be used to make a condition repeat, but only for a finite amount of time.}}

== References ==
<references/>

== See Also ==
* [[If () Then, Else (block)|If () Then, Else]]

{{Control Blocks}}
[[Category:Control Blocks]]
[[de:Falls () (Block)]]
[[ja:もし () なら (ブロック)]]