14.可调用类(Callable classes)
15.Typedefs
16.MetaData
17.注释
18.总结
19.参考资料
1.开发工具 VS Code 常用快捷键
功能 快捷键
代码提示 keymap→搜索 Trigger Suggest 修改成 option + /
参数提示 cmd + shift + space
2.重要概念
一个例子：
// Define a function.
printInteger(int aNumber) {
print('The number is $aNumber.'); //
Print to console.
}
// This is where the app starts executing.
main() {
var number = 42; // Declare and
initialize a variable.
printInteger(number); // Call a
function.
}
Everything you can place in a variable is an , and every object is an instance of a . Even numbers, functions, and are
object
class
null
objects. All objects inherit from the class.Object
Although Dart is strongly typed, type annotations are optional because Dart can infer types. In the code above, is inferred to number
be of type . When you want to explicitly say that no type is expected, .int use the special typedynamic
Dart supports generic types, like (a list of integers) or (a list of objects of any type).List<int> List<dynamic>
Dart supports top-level functions (such as ), as well as functions tied to a class or object ( and , main()
static
instance methods
respectively). You can also create functions within functions ( or ).
nested
local functions
Similarly, Dart supports top-level , as well as variables tied to a class or object (static and instance variables). Instance
variables
variables are sometimes known as fields or properties.
Unlike Java, Dart doesn’t have the keywords , , and . If an identifier starts with an underscore (_), it’s public protected private
private to its library. For details, see .Libraries and visibility
Identifiers
can start with a letter or underscore (_), followed by any combination of those characters plus digits.
Dart has both (which have runtime values) and (which don’t). For example, the
expressions
statements
conditional expressioncondit
has a value of or . Compare that to an , which has no value. A statement ion ? expr1 : expr2 expr1 expr2 if-else statement
often contains one or more expressions, but an expression can’t directly contain a statement.
Dart tools can report two kinds of problems: and . Warnings are just indications that your code might not work, but
warnings
errors
they don’t prevent your program from executing. Errors can be either compile-time or run-time. A compile-time error prevents the
code from executing at all; a run-time error results in an being raised while the code executes.exception
一切皆是对象。包括数字类型、函数类型和 都是对象，所有的对象都继承自 这个类null Object
Dart 是一个强类型语言，支持类型推导，例如上面例子中定义的 类型会被推导成 类型。如果你不想声明成某个确切的类型，你可以使number int
用 dynamic type
Dart 支持泛型，例如 List<int> 或者 List<dynamic>
Dart 支持顶级函数，例如 main(), 你可以在 class 中声明 static 或者 实例方法。你可以再函数中在声明一个函数（嵌套或者叫局部函数）
Dart 也支持定级变量
Dart 没有 public, protected 和 private 这样的关键字，这个区别于 Java。如果一个标志符（变量名、函数名）以下划线( _ )开头，那么他是私有
的
标志符以字符或者( _ ) 开头，后面跟上字符和数字的组合
Dart 既有表达式（有运行时值）又有语句声明（没有运行时值）。例如条件表达式 (condition ? expr1 : expr2) 有值 expr1 或者 expr2，具体值需
要运行时才知道。与 if-else 声明（没有值）。一个语句声明通常包含一个或多个表达式，但是一个表单时不能直接包含一个声明。云里雾里的
Dart 工具可以报出两类问题：警告和错误。警告紧紧是标识你的代码可能不工作，但是不会阻止代码的运行。错误可以是编译时间或者运行时间。
编译错误阻止代码运行，运行时错误会抛出异常
3.关键字段
abstract
2
dynamic
2
implements
2
show
1
as
2
else
import
2
static
2
