while
A while
executes its body as long as its condition is truthy.
while some_condition
do_this
end
The condition is first tested and, if truthy, the body is executed. That is, the body might never be executed.
A while
‘s type is always Nil
.
Similar to an if
, if a while
‘s condition is a variable, the variable is guaranteed to not be nil
inside the body. If the condition is an var.is_a?(Type)
test, var
is guaranteed to be of type Type
inside the body. And if the condition is a var.responds_to?(:method)
, var
is guaranteed to be of a type that responds to that method.
The type of a variable after a while
depends on the type it had before the while
and the type it had before leaving the while
‘s body:
a = 1
while some_condition
# a : Int32 | String
a = "hello"
# a : String
a.size
end
# a : Int32 | String
Checking the condition at the end of a loop
If you need to execute the body at least once and then check for a breaking condition, you can do this:
while true
do_something
break if some_condition
end
Or use loop
, found in the standard library:
loop do
do_something
break if some_condition
end