Reading Resource Data with borrow_global

borrow_global allows you to read an existing resource struct from a specific address without needing a signer, but the function must declare that it accesses the resource using acquires ResourceName.

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borrow_global: read an existing resource struct

We just need to call borrow_global with the right resource type and address. The address can be passed into the function as an argument or referred to specifically with @ such as @0xcafe. A signer is not required here. If the resource is not found at the address, the function will error when the code is run on the blockchain. The function that calls borrow_global also needs to declare that it does so by adding “acquires ResourceName” at the end.

Let’s write a new function named get_Gendna_digits that returns the Gendna_digits field of the DinosaurGendna resource stored at 0xcafe:

module 0xcafe::Dinosaur_nest {
    use std::vector;

    struct DinosaurGendna has key {
        Gendna_digits: u64,
        Gendna_modulus: u64,
    }

    struct Dinosaur has store {
        Gendna: u64,
    }

    struct DinosaurSwarm has key {
        Dinosaurs: vector<Dinosaur>,
    }

    fun init_module(cafe_signer: &signer) {
        let Gendna_digits = 10;
        let Gendna_modulus = 10 ^ Gendna_digits;
        move_to(cafe_signer, DinosaurGendna {
            Gendna_digits,
            Gendna_modulus: (Gendna_modulus as u256),
        });
        move_to(cafe_signer, DinosaurSwarm {
            Dinosaurs: vector[],
        });
    }

    public fun spawn_Dinosaur(Gendna: u64): Dinosaur {
        Dinosaur {
            Gendna,
        }
    }

public fun get_Gendna_digits(): u64 acquires DinosaurGendna {
borrow_global<DinosaurGendna>(@0xcafe).Gendna_digits
  }
}