Expand description
What expression to evaluate when an if
condition evaluates to false
.
else
expressions are optional. When no else expressions are supplied it is assumed to evaluate
to the unit type ()
.
The type that the else
blocks evaluate to must be compatible with the type that the if
block
evaluates to.
As can be seen below, else
must be followed by either: if
, if let
, or a block {}
and it
will return the value of that expression.
let result = if true == false {
"oh no"
} else if "something" == "other thing" {
"oh dear"
} else if let Some(200) = "blarg".parse::<i32>().ok() {
"uh oh"
} else {
println!("Sneaky side effect.");
"phew, nothing's broken"
};
RunHere’s another example but here we do not try and return an expression:
if true == false {
println!("oh no");
} else if "something" == "other thing" {
println!("oh dear");
} else if let Some(200) = "blarg".parse::<i32>().ok() {
println!("uh oh");
} else {
println!("phew, nothing's broken");
}
RunThe above is still an expression but it will always evaluate to ()
.
There is possibly no limit to the number of else
blocks that could follow an if
expression
however if you have several then a match
expression might be preferable.
Read more about control flow in the Rust Book.