journal: Some code accessed the property 'AuthList' on the module 'authList'. That property was defined with 'let' or 'const' inside the module. This was previously supported, but is not correct according to the ES6 standard. Any symbols to be exported from a module must be defined with 'var'. The p roperty access will work as previously for the time being, but please fix your code anyway.

这是一个代码错误信息，它指出一些代码在模块 `authList` 中访问了一个被定义为 `let` 或 `const` 的属性 `AuthList`。按照 ES6 标准，不应该这样定义在模块中导出的属性，应该使用 `var`。因为这是一个不正确的定义方式，所以未来可能会不支持这种方式。虽然当前访问该属性还能正常工作，但是建议尽快将代码修改为符合标准的方式。

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详细举例This code represents a class named "PropertyManagementCompany" which manages a portfolio of real estate properties. The class has a name, liquidity and a set of properties that it manages. The liquidity represents the amount of money the company has available to purchase new properties or sell existing ones. The class has two constructors, one that creates an empty portfolio and sets the liquidity to zero, and another that takes a list of properties and adds them to the portfolio. Both constructors also require the company name and liquidity as parameters. The class has two methods to buy and sell real estate properties. The "buyProperty" method takes a property and a purchase price as parameters and adds the property to the portfolio if the company has enough liquidity to buy it. The "sellProperty" method takes a property and removes it from the portfolio while adding the property's current valuation to the company's liquidity. The class also has getters for the name, liquidity, and portfolio. The "checkName" method is a private helper method that checks if the company name is empty and throws an exception if it is. Overall, this code uses encapsulation to hide the implementation details of the PropertyManagementCompany class. The class has private fields that can only be accessed through its public methods. This approach makes the code more modular and easier to maintain.

class PropertyManagementCompany:
    def __init__(self, name, liquidity, properties=None):
        self.checkName(name)
        self.name = name
        self.liquidity = liquidity
        if properties is None:
            self.portfolio = []
        else:
            self.portfolio = properties

    def buyProperty(self, property, purchasePrice):
        if self.liquidity >= purchasePrice:
            self.portfolio.append(property)
            self.liquidity -= purchasePrice

    def sellProperty(self, property):
        if property in self.portfolio:
            self.portfolio.remove(property)
            self.liquidity += property.currentValuation

    def getName(self):
        return self.name

    def getLiquidity(self):
        return self.liquidity

    def getPortfolio(self):
        return self.portfolio

    def checkName(self, name):
        if name == '':
            raise ValueError('Company name cannot be empty.')

For example, we can create a new PropertyManagementCompany as follows:

properties = [Property('123 Main St.', 100000), Property('456 Oak Ave.', 200000)]
company = PropertyManagementCompany('ABC Company', 500000, properties)

This creates a company named "ABC Company" with $500,000 liquidity and a portfolio containing two properties. We can then buy a new property and sell an existing property using the `buyProperty` and `sellProperty` methods:

newProperty = Property('789 Elm St.', 150000)
company.buyProperty(newProperty, 150000)

propertyToSell = properties[0]
company.sellProperty(propertyToSell)

This would add the new property to the portfolio and remove the first property from the portfolio while adding its current valuation to the company's liquidity.

This simple class contains four instance variables, noting that they are defined as ‘public’. Add more codes as below to instantiate the class Person and initialize some instance variables. class Program { static void Main(string[ ] args) { Person David = new Person(); Person Alice = new Person(); // Initialize David David.age = 21; David.name = "David"; David.weight = 185.4; David.height = 72.3; // Initialize Alice Alice.age = 18; Alice.name = "Alice"; Alice.weight = 125.7; Alice.height = 67.1; // print some values Console.WriteLine("David’s age = {0}; David’s weight = {1}",David.age, David.weight); Console.WriteLine("Alice’s age = {0}; Alice’s weight = {1}", Alice.age, Alice.weight); } } Properties in C#: In the previous, we accessed the characteristics of the Person Class using some public methods such as ‘setXXX(…)’ and ‘getXXX()’. C# gives us a more controlled way to access these data, called properties. Search the internet (‘Baidu’ or ‘Google’) about the property and amend the code above accordingly using the property. (Task 1.3)

class Person
{
public int Age { get; set; }
public string Name { get; set; }
public double Weight { get; set; }
public double Height { get; set; }
}

class Program
{
static void Main(string[] args)
{
Person David = new Person();
Person Alice = new Person();

// Initialize David
David.Age = 21;
David.Name = "David";
David.Weight = 185.4;
David.Height = 72.3;

// Initialize Alice
Alice.Age = 18;
Alice.Name = "Alice";
Alice.Weight = 125.7;
Alice.Height = 67.1;

// Print some values
Console.WriteLine("David’s age = {0}; David’s weight = {1}", David.Age, David.Weight);
Console.WriteLine("Alice’s age = {0}; Alice’s weight = {1}", Alice.Age, Alice.Weight);
}
}

In the modified code, we have replaced the public instance variables with properties in the Person class. Properties provide a more controlled way to access and modify data.

Properties are defined using the `{ get; set; }` syntax. They allow you to get the value of the property using `PropertyName` and set the value using `PropertyName = value`.

In the Main method, we now use the properties `Age`, `Name`, `Weight`, and `Height` to initialize the attributes for David and Alice. When printing the values, we access the property values directly.

Using properties instead of public instance variables provides encapsulation and allows for better control over data access.