| 安装 | 如何安装 dart - 每个语言都要知道如何安装，详情 |
| 变量 Dart Variables | void main() {
// variables
// strings, numbers, booleans, and doubles
var name = "John";
String occupation = "teacher";
var age = 30;
var isMarried = true;
var height = 1.75;
// dynamic variables
dynamic greeting = "Hello";
// greeting = 123; // this is allowed
// const and final variables
// const 与 final 变量
// const 变量的值不能被修改，final 变量的值在初始化之后不能被修改
// 区别在于 运行时常量 和 编译时常量。
const PI = 3.14;
final year = 2024;
print(name);
print(occupation);
print(age);
print(isMarried);
print(height);
print(greeting);
print(PI); // this will give an error because PI is a constant
print(year);
}
|
| 数据类型 Data Types | void main() {
// data types in Dart
// Numbers, Strings, Booleans, Lists, Maps, Sets, Dynamic
// Strings
String name = "John";
print("String: $name");
// Numbers
int age = 25;
double height = 1.75;
print("Int: $age, Double: $height");
// Booleans
bool isMarried = true;
print("Boolean: $isMarried");
// Lists
List<String> fruits = ["Apple", "Banana", "Orange"];
print("List: $fruits");
// Maps
Map<String, int> marks = {"John": 85, "Jane": 90};
print("Map: $marks");
// Sets
Set<int> numbers = {1, 2, 3, 4, 5};
print("Set: $numbers");
// Dynamic
dynamic variable = "Hello";
variable = 10;
print("Dynamic: $variable");
// Get the data type of a variable
print(name.runtimeType);
}
|
| 列表 Dart Lists | void main() {
var numbers = [1, 2, 3, 4, 5];
print(numbers);
print(numbers.length);
print(numbers[0]);
print(numbers[numbers.length - 1]);
numbers.add(6);
print(numbers);
numbers.insert(2, 10);
print(numbers);
numbers.remove(10);
print(numbers);
numbers.removeAt(2);
print(numbers);
numbers.clear();
print(numbers);
}
|
| 字典 Dart Maps | void main() {
// Maps! key-value pairs
var myMap = {"apple": 2, "banana": 4, "orange": 6};
print(myMap);
// show values of the map
print(myMap.values);
// show keys of the map
print(myMap.keys);
// show length of the map
print(myMap.length);
// add a new key-value pair
myMap["grape"] = 8;
print(myMap);
// remove a key-value pair
myMap.remove("banana");
print(myMap);
}
|
| 循环 Loop | void main() {
// For loop
for (int i = 0; i < 5; i++) {
print(i);
}
// For in loop
List<String> fruits = ["apple", "banana", "orange"];
for (String fruit in fruits) {
print(fruit);
}
// for each loop
Map<String, int> scores = {"John": 85, "Jane": 92, "Bob": 78};
for (String name in scores.keys) {
print("$name scored ${scores[name]}");
}
// while loop
int j = 0;
while (j < 5) {
print(j);
j++;
}
}
|
| 流程 Logic | void main() {
// if else statements
int age = 20;
if (age >= 18) {
print("You are old enough to vote.");
} else {
print("You are not old enough to vote.");
}
// if else if statements
int temperature = 25;
if (temperature < 10) {
print("It's too cold outside.");
} else if (temperature < 20) {
print("It's a bit chilly outside.");
} else if (temperature < 30) {
print("It's a bit warm outside.");
} else {
print("It's hot outside.");
}
}
|
| 函数 Functions | void main() {
// without return value
myFunction(){
print("Hello World");
}
myFunction();
// with return value
int add(int a, int b){
return a + b;
}
print(add(2, 3));
}
|
| 用户输入 UserInput | import 'dart:io';
void main() {
String? name = stdin.readLineSync();
print("Hello, $name!");
}
|
| 类型转换 string to int | void main() {
// string to integer conversion
String str = "1234";
int num = int.parse(str);
print(num);
// string to double conversion
String str1 = "3.14159";
double num1 = double.parse(str1);
print(num1);
// integer to string conversion
int num2 = 1234;
String str2 = num2.toString();
print(str2);
}
|
| 类 Class/OOP | // create Person class
class Person {
String? name;
int? age;
// constructor
Person(this.name, this.age);
// method
void greet() {
print("Hello, my name is $name and I am $age years old.");
}
}
void main() {
// create object of Person class
Person person1 = Person("John", 25);
// call method of Person class
person1.greet();
}
|