Casting (type conversion)

Casting to a Float

"123.50".to_f   #=> 123.5
Float("123.50") #=> 123.5

However, there is a difference when the string is not a valid Float:

"something".to_f   #=> 0.0
Float("something") # ArgumentError: invalid value for Float(): "something"

Casting to a String

123.5.to_s    #=> "123.5"
String(123.5) #=> "123.5"

Usually, String() will just call #to_s.

Methods Kernel#sprintf and String#% behave similar to C:

sprintf("%s", 123.5) #=> "123.5"
"%s" % 123.5 #=> "123.5"
"%d" % 123.5 #=> "123"
"%.2f" % 123.5 #=> "123.50"

Casting to an Integer

"123.50".to_i     #=> 123
Integer("123.50") #=> 123

A string will take the value of any integer at its start, but will not take integers from anywhere else:

"123-foo".to_i # => 123
"foo-123".to_i # => 0

However, there is a difference when the string is not a valid Integer:

"something".to_i     #=> 0
Integer("something") # ArgumentError: invalid value for Integer(): "something"

Floats and Integers

1/2 #=> 0

Since we are dividing two integers, the result is an integer. To solve this problem, we need to cast at least one of those to Float:

1.0 / 2      #=> 0.5
1.to_f / 2   #=> 0.5
1 / Float(2) #=> 0.5

Alternatively, fdiv may be used to return the floating point result of division without explicitly casting either operand:

1.fdiv 2 # => 0.5