View source for If () Then (block)

{{block
| name            = If () Then
| image           = if <> then
| sb              = 3.0
| category        = [[Control Blocks|Control]]
| type            = [[C Block|C]]
}}
{{confused|If () Then, Else (block)}}
The '''if () then''' block is a [[Control Blocks|control block]] and a [[C Block|C block]]. If its boolean condition is true, the blocks held inside it will run, and then the [[script]] involved will continue. If the condition is false, the scripts inside the block will be ignored. 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.

Prior to [[Scratch 2.0]], this block was titled '''if ()'''.

== Example Uses ==
The most basic uncertainty in programming is checking conditions. This block is Scratch's main way of doing this; 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

when I receive [jump v]
repeat (6)
    change y by (2)
end
repeat (6)
    change y by (-2)
end
</scratchblocks>

* Making sure a [[list]] contains a specific item

<scratchblocks>
if <not<[list v] contains [1]?>> then
    stop [all v]
end
</scratchblocks>

== Workaround ==
{{main|List of Block Workarounds}}
This block can be replicated by not utilizing the second field in the [[If () Then, Else (block)|If () Then, Else]] block:

<scratchblocks>
if <. . . :: grey> then
    . . .
else
end
</scratchblocks>

Alternatively, this block can be replicated by passing the boolean condition to the [[Repeat () (block)|Repeat ()]] block:
<scratchblocks>
repeat <. . . :: grey>
...
end
</scratchblocks>
This works because if the boolean is true, it will run one time as putting a boolean into a number reporter equals 1, but if the boolean is false, it will repeat zero times which means the script will not run.

== 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>[[topic:14843]]</ref><ref>[[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]] loop or another kind of repetition. The [[Repeat Until ()|repeat until ()]] and [[Repeat ()]] blocks can also be used to make a condition repeat, but only for a finite amount of time.

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

== References ==
<references/>

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