Adding Elements with vector::push_back

vector::push_back allows you to add elements to a vector by passing a mutable reference (&mut), enabling dynamic storage updates within a module.

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`vector::push_back`: add all the things we’ve learned

We can add all the things we’ve learned so far to create a more complex module. One more thing you can do now that you know references: You can add an element to a vector using vector::push_back and pass a mutable reference to the vector.

Let’s modify spawn_dinosaur to add the new Dinosaur to the DinosaurSwarm’s vector of Dinosaurs instead of returning it.


module 0xcafe::dinosaur_nest {
    use std::vector;
 
    struct DinosaurGendna has key {
        gendna_digits: u64,
        gendna_modulus: u256,
    }
 
    struct Dinosaur has store {
        gendna: u64,
    }
 
    struct DinosaurSwarm has key {
        dinosaurs: vector<Dinosaur>,
    }
 
    fun init_module(cafe_signer: &signer) {
        let gendna_digits = 10;
        // 10^10. Move has no exponent operator, so the value is written out.
        let gendna_modulus = 10000000000;
        move_to(cafe_signer, DinosaurGendna {
            gendna_digits: gendna_digits,
            gendna_modulus: (gendna_modulus as u256),
        });
        move_to(cafe_signer, DinosaurSwarm {
            dinosaurs: vector[],
        });
    }
 
    public fun spawn_dinosaur(gendna: u64) acquires DinosaurSwarm {
        let dinosaur = Dinosaur {
            gendna: gendna,
        };
        let dinosaur_swarm = borrow_global_mut<DinosaurSwarm>(@0xcafe);
        vector::push_back(&mut dinosaur_swarm.dinosaurs, dinosaur);
          }
 
    public fun get_gendna_digits(): u64 acquires DinosaurGendna {
        borrow_global<DinosaurGendna>(@0xcafe).gendna_digits
    }
 
    public fun set_gendna_digits(new_gendna_digits: u64) acquires DinosaurGendna {
        let dinosaur_gendna = borrow_global_mut<DinosaurGendna>(@0xcafe);
        dinosaur_gendna.gendna_digits = new_gendna_digits;
    }
 
    public fun get_first_dinosaur_gendna(): u64 acquires DinosaurSwarm {
        let dinosaur_swarm = borrow_global<DinosaurSwarm>(@0xcafe);
        let first_dinosaur = vector::borrow(&dinosaur_swarm.dinosaurs, 0);
        first_dinosaur.gendna
    }
}

Adding Elements with vector::push_back

vector::push_back: add all the things we’ve learned

`vector::push_back`: add all the things we’ve learned