Solidity Struct Demo: Correcting Common Errors and Best Practices

There are several issues with the given code.

1. There is a missing semicolon at the end of the line where the struct is defined.
2. The struct instance ('b') should be defined inside a function or in the global scope, not directly in the contract body.
3. The function names are all the same, which is not allowed. Each function should have a unique name.
4. The return types of the functions are inconsistent. For the last function, the return type should be 'uint', not 'string memory'.

Here's the corrected code:

pragma solidity >=0.7.0 <0.9.0;

contract StructDemo {
    struct Book {
        string Name;
        string publisher;
        uint price;
        uint pagecount;
    }
    
    Book b;
    
    constructor() {
        b = Book('aaa', 'bbb', 12, 13);
    }
    
    function getName() public view returns (string memory) {
        return b.Name;
    }
    
    function getPublisher() public view returns (string memory) {
        return b.publisher;
    }
    
    function getPrice() public view returns (uint) {
        return b.price;
    }
    
    function getPageCount() public view returns (uint) {
        return b.pagecount;
    }
}

In this corrected code:

• The struct instance 'b' is defined inside the contract constructor.
• Each function has a unique name.
• The return types of the functions are consistent with the type of the respective struct member.