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# Boolean Parameter
## Introduction
`Boolean Parameter` is a special case of [Control Couple](Control-Couple.md), where a method parameter is defaulted
to true or false. A _Boolean Parameter_ effectively permits a method's caller
to decide which execution path to take. This is a case of bad cohesion. You're creating a dependency between methods that is not really necessary, thus increasing coupling.
## Example
Given
```Ruby
class Dummy
def hit_the_switch(switch = true)
if switch
puts 'Hitting the switch'
# do other things...
else
puts 'Not hitting the switch'
# do other things...
end
end
end
```
Reek would emit the following warning:
```
test.rb -- 3 warnings:
[1]:Dummy#hit_the_switch has boolean parameter 'switch' (BooleanParameter)
[2]:Dummy#hit_the_switch is controlled by argument switch (ControlParameter)
```
Note that both smells are reported, `Boolean Parameter` and `Control Parameter`.
## Getting rid of the smell
This is highly dependant on your exact architecture, but looking at the example above what you could do is:
* Move everything in the `if` branch into a separate method
* Move everything in the `else` branch into a separate method
* Get rid of the `hit_the_switch` method alltogether
* Make the decision what method to call in the initial caller of `hit_the_switch`
## Current support in Reek
Reek can only detect a Boolean parameter when it has a default initializer like in the example above.
## Configuration
`Boolean Parameter` supports the [Basic Smell Options](Basic-Smell-Options.md).
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17 entries across 17 versions & 1 rubygems