为什么我不能在NEAR合同中阅读此HashMap? [英] Why can't I read this HashMap in a NEAR contract?

问题描述

我有一个NEAR智能合约，该合约保留Veggie记录的HashMap.我最基本的访问器方法get_veggie(vid)查找并返回一条Veggie记录，通过了单元测试，但是在部署的合同中失败.当我发送另一个访问器方法get_veggie_keys()返回的键之一时，它会因蔬菜不存在"而感到恐慌.

I have a NEAR smart contract that keeps a HashMap of Veggie records. My most basic accessor method get_veggie(vid), which looks up and returns one Veggie record, passes unit tests but fails in the deployed contract. It panics with 'veggie does not exist' when I send one of the keys returned by another accessor method, get_veggie_keys().

// this method returns an array of u64 keys:
pub fn get_veggie_keys(&self) -> Vec<TokenId> {
    self.veggies.keys().cloned().collect()
}

// but this method panics when I give it one of those keys:
pub fn get_veggie(&self, vid: TokenId) -> Veggie {
    let veggie = match self.veggies.get(&vid) {
        Some(c) => {
            c
        },
        None => {
            env::panic(b"Veggie does not exist.")
        }
    };
    veggie.clone()
}

当我从NEAR CLI调用这些方法时，我看到了这种现象:

I see this behavior when I call these methods from the NEAR CLI:

% near call --accountId $ACCOUNTID $CONTRACT_NAME get_veggie_keys      
Scheduling a call: dev-1602786511653-5521463.get_veggie_keys()
Transaction Id FdWjevTsMD73eFPno41THrvrChfB9HDoLAozuiXsBwru
To see the transaction in the transaction explorer, please open this url in your browser
https://explorer.testnet.near.org/transactions/FdWjevTsMD73eFPno41THrvrChfB9HDoLAozuiXsBwru
[ 3469591985938534000, [length]: 1 ]
%
% near call --accountId $ACCOUNTID $CONTRACT_NAME get_veggie '{"vid":3469591985938534000}'
Scheduling a call: dev-1602786511653-5521463.get_veggie({"vid":3469591985938534000})
Receipt: 68ahRQyNN7tzAQMbguCEy83ofL6S5mv3iLVmmN2NH8gh
    Failure [dev-1602786511653-5521463]: Error: Smart contract panicked: Veggie does not exist.
An error occured [...]

合同中的这种行为与单元测试中的行为有何不同?我称方法错误吗?我不了解HashMaps吗?感谢您的任何建议.也许我犯了一个Rust noob错误，但是我对此深感困惑...

How is this behavior different in the contract than in unit tests? Am I calling the method wrong? Do I not understand HashMaps? Thanks for any advice. Maybe I'm making a Rust noob error, but I'm deeply puzzled here ...

推荐答案

您正在靠近那里.您将要使用 U64 或 U128 ，它们是特殊的JSON类型.另外，您也不想使用 HashMap ，因为它无法缩放.我在这里创建了一个示例存储库供您查看: https://github.com/mikedotexe/near-stackoverflow-64378144/blob/master/src/lib.rs

You're getting close there. You'll want to use U64 or U128 which are special JSON types. Also, you'll not want to use a HashMap as that doesn't scale. I have created an example repository here for you to see: https://github.com/mikedotexe/near-stackoverflow-64378144/blob/master/src/lib.rs

如果参数要使用需要超过53位的数字，则需要这样做:

If a parameter is going to take a number that requires more than 53 bits you'll need to do it like this:

use near_sdk::json_types::U128;
…
pub fn add_veggie_taste(&mut self, upc: U128, taste: String) {
  …
}

如前所述，您将要使用NEAR集合而不是HashMap.请查看此链接以了解各种选项: https://docs.rs/near-sdk/2.0.0/near_sdk/collections/index.html

As mentioned, you'll want to use a NEAR Collection instead of HashMap. Please see this link for the various options: https://docs.rs/near-sdk/2.0.0/near_sdk/collections/index.html

此外，我相信您可能没有像下面那样在结构上方添加宏.对于单元测试而不是链上测试，这将是有意义的.

Also, I believe you may not have added the macros above your struct as we have below. This would make sense for it working with unit tests but not on-chain.

#[near_bindgen]
#[derive(BorshDeserialize, BorshSerialize)]
pub struct Produce {
    pub veggies_taste: TreeMap<UPC, String>,
    pub veggies_taste2: TreeMap<UPC, String>
}

#[near_bindgen]
impl Produce {
  …
  pub fn add_veggie_taste(&mut self, upc: U128, taste: String) {
    let existing_veggie: Option<String> = self.veggies_taste.get(&upc.into());
    if existing_veggie.is_some() {
      env::panic(b"Sorry, already added this UPC!")
    }
    // Note that "into" turns the U128 (as a string, basically) into u128
    self.veggies_taste.insert(&upc.into(), &taste);
  }
  …
} 

我受到这篇文章的启发，并决定在此处制作视频: https://youtu.be/d68_hw_zjT4

I was inspired by this post and decided to make a video here, as well: https://youtu.be/d68_hw_zjT4

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