maps.md

Maps

0x1::simple_map

This module provides a solution for sorted maps, that is it has the properties that

• Keys point to Values
• Each Key must be unique
• A Key can be found within O(Log N) time
• The data is stored as sorted by Key
• Adds and removals take O(N) time

Defining an empty map:

let NAME : SimpleMap<TYPE1,TYPE2> = simple_map::create();

Operations on maps:

Lets understand various operations on maps using the module given below.

module my_addrx::Mapping
{
    use std::simple_map::{SimpleMap,Self};
    use std::string::{String,utf8};

    public fun mapping_in_move()
    {
        let mp:SimpleMap<u64,String> = simple_map::create(); //creating an empty map where Key->integer and Value->string.
        
        
        //adding the key and corresponding value in the map
        simple_map::add(&mut mp,1 ,utf8(b"John")); 
        simple_map::add(&mut mp,2 ,utf8(b"Ben"));
        simple_map::add(&mut mp,3 ,utf8(b"Tony"));
        simple_map::add(&mut mp,4 ,utf8(b"Gwen"));
      
        //calculating the length of the map
        let l=simple_map::length(&mut mp);
        assert!(l==4,1);

        //checking if a given key exists or not in the vector
        let x=simple_map::contains_key(&mut mp,&2);
        assert!(x==true,1);

        //removing key value pair in the map
        simple_map::remove(&mut mp,&2);
        assert!(simple_map::contains_key(&mut mp,&2)==false,1);

        //borrowing immutable reference to the value of a given key        
        let v=simple_map::borrow(&mut mp,&3);
        assert!(v==&utf8(b"Tony"),1);

        //borrowing mutable reference to the value of a given key        
        let v=simple_map::borrow_mut(&mut mp,&3);
        *v=utf8(b"Changed Name");
        
        assert!(simple_map::borrow(&mut mp,&3)==&utf8(b"Changed Name"),1);


    }

    #[test]
    fun testing()
    {
        mapping_in_move();
    }
}t

{% hint style="info" %} For more information on maps follow this link. {% endhint %}