Add multi asset SRC7 example

examples/src_7/multi_asset/Forc.toml

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+[project]
+authors = ["Fuel Labs <[email protected]>"]
+entry = "multi_asset.sw"
+license = "Apache-2.0"
+name = "multi_src7_asset"
+
+[dependencies]
+src_7 = { path = "../../../standards/src_7" }
+src_20 = { path = "../../../standards/src_20" }

examples/src_7/multi_asset/src/multi_asset.sw

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+contract;
+
+use src_7::{Metadata, SRC7};
+use src_20::SRC20;
+
+use std::{
+    call_frames::contract_id, 
+    hash::Hash,
+    string::String,
+    storage::storage_string::*,
+};
+
+// In this example, all assets minted from this contract have the same decimals, name, and symbol
+configurable {
+    /// The decimals of every asset minted by this contract.
+    DECIMALS: u8 = 0u8,
+    /// The name of every asset minted by this contract.
+    NAME: str[7] = __to_str_array("MyAsset"),
+    /// The symbol of every asset minted by this contract.
+    SYMBOL: str[5] = __to_str_array("MYAST"),
+    /// The metadata for the "social:x" key.
+    SOCIAL_X: str[12] = __to_str_array("fuel_network"),
+    /// The metadata for the "site:forum" key.
+    SITE_FORUM: str[27] = __to_str_array("https://forum.fuel.network/"),
+}
+
+storage {
+    /// The total number of distinguishable assets this contract has minted.
+    total_assets: u64 = 0,
+    /// The total supply of a particular asset.
+    total_supply: StorageMap<AssetId, u64> = StorageMap {},
+    /// The metadata for the "image:svg" key.
+    svg_images: StorageMap<AssetId, StorageString> = StorageMap {},
+    /// The metadata for the "attr:health" key.
+    health_attributes: StorageMap<AssetId, u64> = StorageMap {},
+}
+
+impl SRC7 for Contract {
+    /// Returns metadata for the corresponding `asset` and `key`.
+    ///
+    /// # Arguments
+    ///
+    /// * `asset`: [AssetId] - The asset of which to query the metadata.
+    /// * `key`: [String] - The key to the specific metadata.
+    ///
+    /// # Returns
+    ///
+    /// * [Option<Metadata>] - `Some` metadata that corresponds to the `key` or `None`.
+    ///
+    /// # Reverts
+    ///
+    /// * When the AssetId provided does not match the default SubId.
+    ///
+    /// # Examples
+    ///
+    /// ```sway
+    /// use src_7::{SRC7, Metadata};
+    /// use std::string::String;
+    ///
+    /// fn foo(contract_id: ContractId, asset: AssetId) {
+    ///     let contract_abi = abi(SRC7, contract_id);
+    ///     let key = String::from_ascii_str("social:x");
+    ///     let data = contract_abi.metadata(asset, key);
+    ///     assert(data.unwrap() == Metadata::String(String::from_ascii_str("fuel_network")));
+    /// }
+    /// ```
+    #[storage(read)]
+    fn metadata(asset: AssetId, key: String) -> Option<Metadata> {
+        require(asset == AssetId::default(contract_id()), "Invalid AssetId provided");
+
+        if key == String::from_ascii_str("social:x") {
+            Some(Metadata::String(String::from_ascii_str(from_str_array(SOCIAL_X))))
+        } else if key == String::from_ascii_str("site:forum") {
+            Some(Metadata::String(String::from_ascii_str(from_str_array(SITE_FORUM))))
+        } else if key == String::from_ascii_str("image:svg") {
+            let svg_image = storage.svg_images.get(asset).read_slice();
+
+            match svg_image {
+                Some(svg) => Some(Metadata::String(svg)),
+                None => None,
+            }
+        } else if key == String::from_ascii_str("attr:health") {
+            let health_attribute = storage.health_attributes.get(asset).try_read();
+
+            match health_attribute {
+                Some(health) => Some(Metadata::Int(health)),
+                None => None,
+            }
+        } else {
+            None
+        }
+    }
+}
+
+// SRC7 extends SRC20, so this must be included
+impl SRC20 for Contract {
+    #[storage(read)]
+    fn total_assets() -> u64 {
+        storage.total_assets.read()
+    }
+
+    #[storage(read)]
+    fn total_supply(asset: AssetId) -> Option<u64> {
+        storage.total_supply.get(asset).try_read()
+    }
+
+    #[storage(read)]
+    fn name(asset: AssetId) -> Option<String> {
+        if asset == AssetId::default(contract_id()) {
+            Some(String::from_ascii_str(from_str_array(NAME)))
+        } else {
+            None
+        }
+    }
+
+    #[storage(read)]
+    fn symbol(asset: AssetId) -> Option<String> {
+        if asset == AssetId::default(contract_id()) {
+            Some(String::from_ascii_str(from_str_array(SYMBOL)))
+        } else {
+            None
+        }
+    }
+
+    #[storage(read)]
+    fn decimals(asset: AssetId) -> Option<u8> {
+        if asset == AssetId::default(contract_id()) {
+            Some(DECIMALS)
+        } else {
+            None
+        }
+    }
+}