从近合同中调用第二份合同(生锈)

Question

在NEARprotocol上，我想从合同(Rust)中调用另一个合同。我试过env::Promise，但无法检索呼叫应答。这里的正确方法是什么？另外，near-sdk机箱文档给出了示例&"bob_near".to_string()，这等同于id bob.near还是一个错误？

以下是我的代码的相关摘录：

near_sdk::setup_alloc!();

#[ext_contract]
pub trait AEXToken {
    fn collect_premie(&mut self, account_id: ValidAccountId) -> bool;
    fn get_min_balance(&self) -> u128;
}
#[near_bindgen]
#[derive(BorshDeserialize, BorshSerialize, PanicOnDefault)]
pub struct Contract {
    tokens: NonFungibleToken,
    metadata: LazyOption<NFTContractMetadata>,
    aex_tokenId: ValidAccountId,
}

#[near_bindgen]
impl Contract {
    pub fn nft_mint(&mut self) -> Token {
        let amount: Balance = env::attached_deposit();
        aex_token::get_min_balance(&self.aex_tokenId.to_string(), 0, 1_000);
        let min_balance: u128 = env::promise_return(1);
        assert!(min_balance < amount);

Answer 1

我想你误解了这件事的运作方式。承诺不会在同样的方法中返回。它在随后的一些块中执行，尽可能快地执行，这取决于网络拥塞，通常在一个块内。

返回值将以回调的形式落在另一个方法中。请参阅此示例以及与SDK位于同一个examples文件夹中的其他几个

呼喊

/// Call functions a, b, and c asynchronously and handle results with `handle_callbacks`.
pub fn call_all(fail_b: bool, c_value: u8) -> Promise {
    let gas_per_promise = env::prepaid_gas() / 5;
    ext::a(env::current_account_id(), 0, gas_per_promise)
        .and(ext::b(fail_b, env::current_account_id(), 0, gas_per_promise))
        .and(ext::c(c_value, env::current_account_id(), 0, gas_per_promise))
        .then(ext::handle_callbacks(env::current_account_id(), 0, gas_per_promise))
}

接收回叫

/// Receives the callbacks from the other promises called.
#[private]
pub fn handle_callbacks(
    #[callback_unwrap] a: u8,
    #[callback_result] b: Result<String, PromiseError>,
    #[callback_result] c: Result<u8, PromiseError>,
) -> (bool, bool) {
    require!(a == A_VALUE, "Promise returned incorrect value");
    if let Ok(s) = b.as_ref() {
        require!(s == "Some string");
    }
    (b.is_err(), c.is_err())
}

这可能有助于更多的解释，https://www.near-sdk.io/cross-contract/callbacks

所以你的呼唤

aex_token::get_min_balance(&self.aex_tokenId.to_string(), 0, 1_000);

应该使用then将其链接到执行此检查的回调。

let min_balance: u128 = env::promise_return(1);
assert!(min_balance < amount);