英文:
In ethers.js, why does the return value of a function return an array containing the value instead of the value?
问题
以下是要翻译的内容：
The assertion for the following test fails:
以下测试的断言失败：
it('should access MAX_COUNT', async () => {
const maxCount = await myContract.functions.MAX_COUNT();
expect(maxCount).to equal(64);
});
With the following error:
出现以下错误：
AssertionError: expected [ BigNumber { value: "64" } ] to equal 64
This is the solidity code for (the concise version of) the smart contract being tested:
这是被测试的智能合约（简化版本）的Solidity代码：
// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;
contract MyContract
{
uint256 public constant MAX_COUNT = 64;
}
Why is the return value [ BigNumber { value: "64" } ] instead of just BigNumber { value: "64" }?
为什么返回值是 [ BigNumber { value: "64" } ] 而不只是 BigNumber { value: "64" }？
英文:
The assertion for the following test fails:
it('should access MAX_COUNT', async () => {
const maxCount = await myContract.functions.MAX_COUNT();
expect(maxCount).to.equal(64);
});
With the following error:
AssertionError: expected [ BigNumber { value: "64" } ] to equal 64
This is the solidity code for (the concise version of) the smart contract being tested:
// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;
contract MyContract
{
uint256 public constant MAX_COUNT = 64;
}
Why is the return value [ BigNumber { value: "64" } ] instead of just BigNumber { value: "64" }?
For context, this question was originally created while trying to figure out this one:
How to correctly import @nomicfoundation/hardhat-chai-matchers into hardhat project? ...
However turns out to be completely unrelated.
答案1
得分: 2
这个测试应该失败：
it('应该访问MAX_COUNT', async () => {
const maxCount = await multiSend.functions.MAX_COUNT();
expect(maxCount).to.equal(64);
});
然而，这个应该通过：
it('应该访问MAX_COUNT', async () => {
const maxCount = await multiSend.MAX_COUNT();
expect(maxCount).to.equal(64);
});
而且这个测试也应该通过：
it('应该访问MAX_COUNT', async () => {
const [maxCount] = await multiSend.functions.MAX_COUNT();
expect(maxCount).to.equal(64);
});
线索在文档中，具体来说是通过Contract.functions.XYZ()与Contract.XYZ()调用时返回类型之间的差异：
总结一下，Contract.XYZ()返回的是Promise<any>或Promise<Result>；而Contract.functions.XYZ()始终返回Promise<Result>
Result对象设计用于可以返回多个值等的函数，这就是为什么需要对其进行数组解构。
英文:
This test should fail:
it('should access MAX_COUNT', async () => {
const maxCount = await multiSend.functions.MAX_COUNT();
expect(maxCount).to.equal(64);
});
However, this should pass:
it('should access MAX_COUNT', async () => {
const maxCount = await multiSend.MAX_COUNT();
expect(maxCount).to.equal(64);
});
And this test should pass too:
it('should access MAX_COUNT', async () => {
const [maxCount] = await multiSend.functions.MAX_COUNT();
expect(maxCount).to.equal(64);
});
The clue is in the documentation,
specifically the difference between the return types
when called via Contract.functions.XYZ() vs Contract.XYZ():
docs for Contract.functions call
In summary Contract.XYZ() returns either Promise< any > or Promise< Result >;
whereas Contract.functions.XYZ() always returns Promise< Result >
The Result object is designed for functions that can return multiple values etc, so that's why it it needs to be array-destructured.
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