VietMX Staff asked 3 years ago
Problem
Given:
x = "hello"Explain the difference between:
x += " world"and
x.concat " world"The += operator re-initializes the variable with a new value, so a += b is equivalent to a = a + b.
Therefore, while it may seem that += is mutating the value, it’s actually creating a new object and pointing the the old variable to that new object.
This is perhaps easier to understand if written as follows:
foo = "foo"
foo2 = foo
foo.concat "bar"
puts foo
=> "foobar"
puts foo2
=> "foobar"
foo += "baz"
puts foo
=> "foobarbaz"
puts foo2
=> "foobar"(Examining the object_id of foo and foo2 will also demonstrate that new objects are being created.)
The difference has implications for performance and also has different mutation behavior than one might expect.
