Deciding between arrays and mappings

Arrays and mappings in solidity are the most commonly used data types to store complex data. There are trade-offs in using one over the other, and each has its own advantages. In this recipe, you will learn about common use cases for arrays and mappings.

How to do it...

Arrays and mappings are used for a series of objects, all of which are the same size and type. Arrays store data sequentially with an incrementing index, whereas mappings store data as key-value pairs (which can also be seen as hash tables).

Arrays

Follow these steps to create arrays in solidity and to perform read/write operations:

1. Arrays can be created with a fixed or dynamic length. Arrays can also hold user-defined types:

uint[10] numbers;

struct Person {
    uint id;
    string name;
}
Person[] candidates;

2. The creation of multidimensional arrays is supported by solidity:

// array of 3 dynamic arrays of bool
bool[][3] table;

Note that the index value is reversed when compared with other languages...