Solidity why the used function is placed before the brace when define a new function

Question

I saw a example for defining Token using  ERC721:

pragma solidity ^0.4.17;

import "./ERC721/ERC721Token.sol";

/**

* @title Repository of ERC721 Deeds

* This contract contains the list of deeds registered by users.

* This is a demo to show how tokens (deeds) can be minted and added

* to the repository.

*/

contract DeedRepository is ERC721Token {

/**

* @dev Created a DeedRepository with a name and symbol

* @param _name string represents the name of the repository

* @param _symbol string represents the symbol of the repository

*/

function DeedRepository(string _name, string _symbol)

public ERC721Token(_name, _symbol) {}

....

I have two questions:

1. Is the function DeedRepository a constructor? This method of defining a constructor with the same name as the contract has been obsoleted, hasn't it?

2. why "ERC721Token(_name, _symbol)" is before the brace "{}"? Here "ERC721Token" is a function that has been defined in ERC721Token. I think the function should be in the braces, like:

function DeedRepository(string _name, string _symbol) public{
ERC721Token(_name, _symbol)
}

shouldn't it?

Answer 1

Hey there!

1. Yes, using the same name for the constructor as that of the class name is obsoleted and the compiler would show an error if it was used. However, this happened since solidity version 0.4.22. So the older versions still allow constructor name to be same as the class name.

2. I think it is outside the braces because that is the syntax to use a class which is a direct implementation of the token. I am not sure about other reasons.

Comments

Thanks for your answer. It's really helpful. Will it work if i use the function ERC721Token inside the braces?

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I don't think so. If you mention it inside the braces then it will a function called inside the DeedRepository function. But what we want is that the DeedRepository should be an implementation of the token.

May I know why do you want to put it inside the braces.

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I now realize what you mean. I always thought ERC721Token is a function instead of a token itself. Thanks for your answer, It's really helpful.

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Yes, that's what I meant. It was confusing to me also at first. I did some research and realized that its the implementation. Is there any particular reason you wanted to use that code inside the braces?

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No, I don't have any particular reason to use that code inside the braces. I just thought it was the right way to put it in braces. Thanks again!