Dart函数

Functions are an essential part of programming and play a crucial role in organizing and reusing code. Think of a function as a set of instructions that perform a specific task. Instead of writing the same code over and over, you can define a function and call it whenever you need that task to be executed.

函数是编程的重要组成部分，在组织和重用代码方面起着至关重要的作用。可以把函数看作是执行特定任务的一组指令。您可以定义一个函数，并在需要执行该任务时调用它，而不是一遍又一遍地编写相同的代码。

You can create a function using the void keyword (if it doesn’t return any value) followed by the function name, parentheses for parameters (if any), and curly braces to enclose the function body.

你可以使用' void '关键字(如果它不返回任何值)创建一个函数，后面跟着函数名，参数括号(如果有)和花括号来括住函数体。

Let’s look at an example to understand functions better:

让我们看一个例子来更好地理解函数:

// Function to greet a personvoid greetPerson(String name) {print(‘Hello, $name! How are you today?’);}

// Function to calculate the sum of two numbersint calculateSum(int a, int b) {return a + b;}

void main() { // Calling the greetPerson function greetPerson(‘John’); // Calling the calculateSum function and storing the result in a variable int result = calculateSum(10, 20); print(‘The sum is: $result’);}

In this example, we have defined two functions: greetPerson and calculateSum. The greetPerson function takes a name as a parameter and greets the person using their name. The calculateSum function takes two parameters a and b, calculates their sum, and returns the result. The return keyword here is like a messenger that allows a function to send back a specific result or value after it has completed its task. It’s like the function saying, “Here’s what I found or calculated, and now you can use this information elsewhere in your code.”

在这个例子中，我们定义了两个函数:' greetPerson '和' calculateSum '。' greetPerson '函数以' name '作为参数，并使用他们的名字向该人打招呼。' calculateSum '函数接受两个参数' a '和' b '，计算它们的和，并返回结果。这里的“return”关键字就像一个信使，允许函数在完成任务后返回特定的结果或值。这就像函数说:“这是我发现或计算的结果，现在您可以在代码的其他地方使用这些信息。”

In the main function, we call the greetPerson function with the argument ‘John’, which prints ‘Hello, John! How are you today?’ to the console. Then, we call the calculateSum function with arguments 10 and 20 and store the result in the variable result. Finally, we print ‘The sum is: 30’ to the console.

在' main '函数中，我们用' John '参数调用' greetPerson '函数，输出' Hello, John!你今天好吗?对着控制台说。然后，我们使用参数10和20调用' calculateSum '函数，并将结果存储在变量' result '中。最后，我们向控制台输出' The sum is: 30 '。

As a note, a function argument in programming is like a special instruction or piece of information that you can give to a function, helping it perform a specific task or calculation. Functions make code more organized, easier to maintain, and promote code reusability. You can define functions for various tasks in your program, making it more efficient and modular.

需要注意的是，编程中的函数参数就像一个特殊的指令或信息片段，您可以给函数，帮助它执行特定的任务或计算。函数使代码更有组织，更易于维护，并提高了代码的可重用性。您可以为程序中的各种任务定义函数，使其更高效和模块化。

While functions have a wide range of use cases and are fundamental to programming, we won’t go into a deep dive into them in this book. Our primary focus is on modern UI development using Flutter.

虽然函数有广泛的用例，并且是编程的基础，但我们不会在本书中深入研究它们。我们主要关注的是使用Flutter进行现代UI开发。

However, understanding functions is essential for building interactive and dynamic user interfaces. Functions play a significant role in organizing your code and making it more maintainable, efficient, and reusable. As we progress through this book, we’ll utilize functions when necessary to enhance the UI development process and create engaging user experiences.

然而，理解函数对于构建交互式和动态用户界面至关重要。函数在组织代码并使其更具可维护性、效率和可重用性方面发挥着重要作用。随着本书的进展，我们将在必要时利用函数来增强UI开发过程并创建引人入胜的用户体验。

示例代码:

int add(int a, int b) { return a + b;}

void main() { int sum = add(33, 333); print(sum);}

输出:

366