How do I get the number of elements in a mapping?

Question

Is there a way for me to get the total number of elements in a mapping in Solidity?

Not unless you count it by yourself (increment after the creation of a new entry, decrement after the deletion of an existing entry). — sea212, Apr 05 '20 at 22:43
Does this help? Are there well-solved and simple storage patterns for Solidity? — Paul Razvan Berg, Nov 06 '21 at 13:28

score 5 · Answer 1 · answered Apr 04 '20 at 20:51

5

You can't. There is no way to know how many entries there are in a mapping.

If you need to keep tract of the mapping's elements you can use a separate array which holds extra information about the mapping elements

answered Apr 04 '20 at 20:51

Lauri Peltonen

score 0 · Answer 2 · answered Nov 06 '21 at 13:20

0

You cannot do it as @Lauri mentioned. You can check how to do it manually in my answer here.

answered Nov 06 '21 at 13:20

2 Answers2