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The Adder SC

The Adder smart contract is a simple smart contract with an add functionality and a global variable that can be incremented.

/// One of the simplest smart contracts possible,
/// it holds a single variable in storage, which anyone can increment.
#[multiversx_sc::contract]
pub trait Adder {
    #[view(getSum)]
    #[storage_mapper("sum")]
    fn sum(&self) -> SingleValueMapper<BigUint>;

    #[init]
    fn init(&self, initial_value: BigUint) {
        self.sum().set(initial_value);
    }

    #[upgrade]
    fn upgrade(&self, initial_value: BigUint) {
        self.init(initial_value);
    }

    /// Add desired amount to the storage variable.
    #[endpoint]
    fn add(&self, value: BigUint) {
        self.sum().update(|sum| *sum += value);
    }
}

We notice 4 functions:

  • sum - this is a global variable, a SingleValueMapper (a single value) of type BigUint (unsigned integer);
  • init - the constructor;
  • add - function that increments the global variable (sum) with the value parameter;
  • upgrade - function executed when upgrading the contract.

We notice 5 types of annotations:

  • #[view(getSum)] - this is a function that allows you to read the storage variable by calling the function getSum;
  • #[storage_mapper("sum")] - this is a global variable (also called a storage) stored at the contract address;
  • #[init] - the constructor function; this is called when deploying the contract;
  • #[upgrade] - this function is called when upgrading the contract;
  • #[endpoint] - an endpoint is a function callable directly by the user; A function not having this annotation will not be exposed publicly.

Here is the smart contract code listed above and here are all the files needed for compilation.

You can obtain the adder smart contract code directly using the following command:

sc-meta new --template adder

Let's build the smart contract, running the next command in the contract root:

sc-meta all build

Below, it is the output of the command:

 /home/adder

Found 1 contract crates.

(1/1)
In /home/adder/meta
Calling `cargo run build`
   Compiling syn v2.0.110
   Compiling serde_core v1.0.228
   Compiling num-traits v0.2.19
   Compiling bitflags v2.10.0
   Compiling hex v0.4.3
   Compiling equivalent v1.0.2
   Compiling utf8parse v0.2.2
   Compiling unwrap-infallible v0.1.5
   Compiling hashbrown v0.16.0
   Compiling arrayvec v0.7.6
   Compiling typenum v1.19.0
   Compiling semver v1.0.27
   Compiling anstyle-query v1.1.4
   Compiling memchr v2.7.6
   Compiling anstyle-parse v0.2.7
   Compiling colorchoice v1.0.4
   Compiling is_terminal_polyfill v1.70.2
   Compiling leb128fmt v0.1.0
   Compiling foldhash v0.1.5
   Compiling anstyle v1.0.13
   Compiling unicode-width v0.2.2
   Compiling serde_json v1.0.145
   Compiling wasm-encoder v0.240.0
   Compiling winnow v0.7.13
   Compiling hex-literal v1.1.0
   Compiling anstream v0.6.21
   Compiling strsim v0.11.1
   Compiling bumpalo v3.19.0
   Compiling clap_lex v0.7.6
   Compiling anyhow v1.0.100
   Compiling ryu v1.0.20
   Compiling clap_builder v4.5.51
   Compiling toml_writer v1.0.4
   Compiling generic-array v1.3.5
   Compiling itoa v1.0.15
   Compiling unicode-segmentation v1.12.0
   Compiling termcolor v1.4.1
   Compiling rustc_version v0.4.1
   Compiling lazy_static v1.5.0
   Compiling colored v3.0.0
   Compiling num-integer v0.1.46
   Compiling convert_case v0.8.0
   Compiling num-bigint v0.4.6
   Compiling wast v240.0.0
   Compiling toml_parser v1.0.4
   Compiling indexmap v2.12.0
   Compiling serde_spanned v1.0.3
   Compiling toml_datetime v0.7.3
   Compiling toml v0.9.8
   Compiling multiversx-sc-codec-derive v0.23.1
   Compiling serde_derive v1.0.228
   Compiling multiversx-sc-derive v0.62.1
   Compiling clap_derive v4.5.49
   Compiling multiversx-sc-codec v0.23.1
   Compiling clap v4.5.51
   Compiling multiversx-chain-core v0.19.1
   Compiling multiversx-sc v0.62.1
   Compiling serde v1.0.228
   Compiling hashbrown v0.15.5
   Compiling wat v1.240.0
   Compiling wasmparser v0.239.0
   Compiling adder v0.0.0 (/home/adder)
   Compiling wasmprinter v0.239.0
   Compiling multiversx-sc-meta-lib v0.62.1
   Compiling adder-meta v0.0.0 (/home/adder/meta)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 13.82s
     Running `/home/adder/target/debug/adder-meta build`
Using workspace target directory: /home/adder/target ...
Building adder.wasm in /home/adder/wasm ...
RUSTFLAGS="-C link-arg=-s -C link-arg=-zstack-size=131072" cargo build --target=wasm32v1-none --release --target-dir /home/adder/target
    Updating crates.io index
    Blocking waiting for file lock on package cache
     Locking 25 packages to latest compatible versions
    Blocking waiting for file lock on package cache
   Compiling proc-macro2 v1.0.103
   Compiling unicode-ident v1.0.22
   Compiling quote v1.0.42
   Compiling hex v0.4.3
   Compiling smallvec v1.15.1
   Compiling typenum v1.19.0
   Compiling rustversion v1.0.22
   Compiling autocfg v1.5.0
   Compiling bitflags v2.10.0
   Compiling endian-type v0.2.0
   Compiling unwrap-infallible v0.1.5
   Compiling arrayvec v0.7.6
   Compiling hex-literal v1.1.0
   Compiling num-traits v0.2.19
   Compiling nibble_vec v0.1.0
   Compiling radix_trie v0.3.0
   Compiling syn v2.0.110
   Compiling generic-array v1.3.5
   Compiling multiversx-sc-codec-derive v0.23.1
   Compiling multiversx-sc-derive v0.62.1
   Compiling multiversx-sc-codec v0.23.1
   Compiling multiversx-chain-core v0.19.1
   Compiling multiversx-sc v0.62.1
   Compiling adder v0.0.0 (/home/adder)
   Compiling multiversx-sc-wasm-adapter v0.62.1
   Compiling adder-wasm v0.0.0 (/home/adder/wasm)
    Finished `release` profile [optimized] target(s) in 8.55s
Copying /home/adder/target/wasm32v1-none/release/adder_wasm.wasm to ../output/adder.wasm ...
Calling wasm-opt on ../output/adder.wasm ...
Extracting imports to ../output/adder.imports.json ...
Checking EI version: 1.5 ... OK
Packing ../output/adder.mxsc.json ...
Contract size: 700 bytes.

Let's check the contract:

ls -l output/
total 16
-rw-rw-r-- 1 user user 1727 nov 13 15:09 adder.abi.json
-rw-rw-r-- 1 user user  262 nov 13 15:09 adder.imports.json
-rw-rw-r-- 1 user user 4078 nov 13 15:09 adder.mxsc.json
-rwxrwxr-x 1 user user  700 nov 13 15:09 adder.wasm

We notice that the resulted contract (adder.wasm) has 700 bytes.

Practice​

  • Compile the Adder contract.