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Dart 入门-1

2018/11/17 Dart

概述

参考 ： https://codelabs.flutter-io.cn/codelabs/from-java-to-dart-cn/index.html#0

Dart 是 Flutter 的主要开发语言 (前提 Java 开发者)

引入的知识

  • 如何创建构造函数
  • 用不同方法指定参数
  • 如何正确地创建 getter 和 setter 方法
  • Dart 如何处理可访问特性
  • 如何使用 Dart 创建工厂模式
  • Dart 中的函数式编程
  • 有关 Dart 其他的一些核心概念

在线编辑工具：

https://dartpad.cn/

开始

定义 Bicycle 类

https://codelabs.flutter-io.cn/codelabs/from-java-to-dart-cn/index.html#1

class Bicycle {
  int cadence;
  int speed;
  Int get speed => _speed;
  int gear;
}

void main() {
}

新增构造函数


class Bicycle {
  int cadence;
  int speed;
  int gear;

	//Bicycle(this.cadence, this.speed, this.gear);

//与上面的等价
	Bicycle(int cadence, int speed, int gear) {
  this.cadence = cadence;
  this.speed = speed;
  this.gear = gear;
	}
}

//验证
void main() {
	var bike = new Bicycle(2, 0, 1);
  print(bike.cadence);
}

优化输出信息


class Bicycle {
  int cadence;
  int speed;
  int gear;

	//Bicycle(this.cadence, this.speed, this.gear);

//与上面的等价
	Bicycle(int cadence, int speed, int gear) {
  this.cadence = cadence;
  this.speed = speed;
  this.gear = gear;
	}


 @override
 String toString() => 'Bicycle: $speed mph';
}

//验证
void main() {
	var bike = new Bicycle(2, 1, 1);
  print(bike.toString());
}

只读变量

将 speed 变量 改造为 私有变量

class Bicycle {
  int cadence;
	//私有变量仅在库内部可见
  int _speed = 10;
  int gear;

	//Bicycle(this.cadence, this.speed, this.gear);

//与上面的等价
	Bicycle(int cadence, int gear) {
  this.cadence = cadence;
  this.gear = gear;
	}

   void applyBrake(int decrement) {
    _speed -= decrement;
  }

  void speedUp(int increment) {
    _speed += increment;
  }

  //getter 方法
  int get speed => _speed;

	@override
 String toString() => 'Bicycle: $_speed mph';
}

//验证
void main() {
	var bike = new Bicycle(2, 1);
  print(bike.toString());
  print(bike._speed);
  bike._speed = 100;
  print(bike._speed);
}

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