Question

Why do these snippets of code behave differently? I thought they were supposed to do the same thing…

    foo = {}
    array = []

    foo['a'] = "1"
    foo['b'] = "2"

    array << foo

    foo['a'] = "3"
    foo['b'] = "4"

    array << foo

    output => [{"a"=>"3", "b"=>"4"}, {"a"=>"3", "b"=>"4"}]

This is not what I want. Fortunately, I tried using this format, which works:

    foo = {}
    array = []

    foo = {
        :a => "1",
        :b => "2"
    }

    array << foo

    foo = {
        :a => "3",
        :b => "4"
    }

    array << foo

    output => [{:a=>"1", :b=>"2"}, {:a=>"3", :b=>"4"}]

What’s going on here?

Answer 1

It’s not " vs. : — it’s that you’re modifying foo (foo[...]=...) in the first example while you’re reassigning the variable foo (foo=...) in the second. In the first example, foo still refers to the same object (which is also in the array) after you put in the values 3 & 4.

For a solution, I recommend the second option (which you can use with '/" (strings) or : (symbols), no matter), or alternatively you can do array << foo.clone to push a copy of foo onto the array, so further modifications won’t change it.