dart学习 之旅

https://dart.dev/guides/language/language-tour

//基本的dart程序
// Define a function.
void printInteger(int aNumber) {
  print('The number is $aNumber.'); // Print to console.
}

// This is where the app starts executing.
void main() {
  var number = 42; // Declare and initialize a variable.
  printInteger(number); // Call a function.
}

// 表示lineCount默认为空值

int? lineCount; 

//late 变量的使用
late String description;

void main() {
  description = 'Feijoada!';
  print(description);
}

Final and const

实例变量只能是Final

Dart常用内置数据类型：

• Numbers (int, double)
• Strings (String)
• Booleans (bool)
• Lists (List, also known as arrays) 范型的用法 循环
• Sets (Set)
• Maps (Map)
• Runes Runes代表字符串的UTF-32字符集, Unicode为每一个字符、标点符号、表情符号等都定义了一个唯一的数值

  runesDemo() {
    Runes runes = new Runes('\u2665, \u{1f605}, \u{1f60e}');
    print(runes);
    print(new String.fromCharCodes(runes));
  }

• The value null (Null)

其他数据类型：Object，Future and Stream（用于异步操作），Iterable，dynamic，void。

Lists    初始化：var list = [1, 2, 3];

Sets

var names = <String>{};
// Set<String> names = {}; // This works, too.
// var names = {}; // Creates a map, not a set.

函数

enableFlags(paramName: value, hidden: false);

可选参数：String say(String from, String msg, [String? device])

缺省参数值：void enableFlags({bool bold = false, bool hidden = false}) {...}

//将函数做为参数
void printElement(int element) {
  print(element);
}

var list = [1, 2, 3];

// Pass printElement as a parameter.
list.forEach(printElement);

条件表达式：

condition ? expr1 : expr2

expr1 ?? expr2

连续操作运算符（级连）

var paint = Paint()
  ..color = Colors.black
  ..strokeCap = StrokeCap.round
  ..strokeWidth = 5.0;

//类的定义
class Point {
  double x = 0;
  double y = 0;

  // Syntactic sugar for setting x and y
  // before the constructor body runs.
  Point(this.x, this.y);
}

类的继承

mixins的用法？？