(ethereum/solidity/truffle) 从测试/客户问题调用智能合约方法

Question

I am taking a udemy course and I encounter a code like this

https://github.com/acloudfan/Blockchain-Course-Basic-Solidity/blob/93ca256bcf8c436c144425291257dcff5c3b269f/test/constants_payable.js#L45

I am confuse why the call to a method is called directly instead of using.call or something, wherein if I do google, the way to call a method of a contract is either using.call or.send but at this point the author just calls it directly, is this allowed, why?

here is the contract code https://github.com/acloudfan/Blockchain-Course-Basic-Solidity/blob/master/contracts/ConstantsPayable.sol

More or less, what is the context of calling smart contract method from a truffle test here? is it like the real environment where it waits for the transaction to be mined before returning or do tests just directly calls it like an ordinary function?

I am posting it here since the author of the udemy course is non responsive and its almost a week and more than a dozen Q&A question are not answered, so the author probably is busy or forgets about the course already (as it is kinda old course but reviewed well).

Answer 1

Before Truffle returns the contract instance ( line 41 ), it uses the ABI interface (provided by the Solidity compiler) to build a map of JS functions for interacting with the contract, including receiveEthers() .

what is the context of calling smart contract method from a truffle test here

Even though Truffle JS tests can be connected to a public testnet or mainnet, it's usually used together with another Truffle tool - local EVM and blockchain emulator called Ganache (see the config file where the author defines connection to a local blockchain). By default, Ganache mines a block after each transaction so that you (as a developer or a tester) don't need to worry about mining and other processes in setting up the network, and the response from the local blockchain it returned almost instantly.

if I do google, the way to call a method of a contract is either using.call or.send

Answering only about Truffle. Other packages such as Web3js or Ethers.js might have slightly different rules. And there are .call() and .send() methods in Solidity (for interacting with other contracts or addresses), that also behave differently than explained here:

You can interact with a contract in two different ways:

• transactions (can make state changes - change contract storage, emit events)
• calls (only read the contract data - no state changes)

By default, if you don't specify whether you want to make a transaction or a call, Truffle makes a transaction . You can override this decision and make a call instead by using the .call() method.

The .send() method is only used for low-level built transactions. A common use case is sending ETH - you need to build the transaction data field, fill the (ETH) value , and call the .send() method (assuming you have configured Truffle to use your private key to sign the transaction).