When we talk about arrays we usually mean the vector of something – primitives, objects or even arrays. But there are a lot of situation when we need to carry extra information with our data. We can use nested arrays but it doesn’t cause that the specific item within the array will be easy to identify. To achieve it we should use custom keys. They provide easy access to any element of the array as long as we know the key corresponding with that value.
There are some reasons why we can use associative arrays instead of simple vectors, e.g. readability. Named keys are also more meaningful than numeric indexes. Instead of thinking about the whys, image the situation when we could use a hashmap. Let’s focus on how we can build the associative array from a vector.