1. 變量聲明
如何定義變量
var name = 'Bob';
變量的初始值
int lineCount;
assert(lineCount == null); // Variables (even numbers) are initially null.
可以使用var，也可以直接指定類型。
final， 定義為final的變量，值不能夠被更改
final name = 'Bob'; // Or: final String name = 'Bob';
name = 'Alice'; // ERROR
2. 基礎類型
字符串
字符串可以使用單引號或者雙引號。
var s1 = 'Single quotes work well for string literals.';
var s2 = "Double quotes work just as well.";
在字符串中，可以直接應用值， ${表達式}， 如果只是一個變量，就可以去掉{}
var s = 'string interpolation';
assert('Dart has $s, which is very handy.' ==
'Dart has string interpolation, which is very handy.');
assert('That deserves all caps. ${s.toUpperCase()} is very handy!' ==
'That deserves all caps. STRING INTERPOLATION is very handy!');
多行字符串，會被認為默認拼接。
var s = 'String ''concatenation'
" works even over line breaks.";
assert(s == 'String concatenation works even over line breaks.');
如果要使用多行字符串，可以這樣, 用'''
var s1 = '''
You can create
multi-line strings like this one.
''';
創建一個不考慮轉義的字符串
var s = @"In a raw string, even /n isn't special.";
StringBuffer, 非常類似.net中的。
var sb = new StringBuffer();
sb.add("Use a StringBuffer ");
sb.addAll(["for ", "efficient ", "string ", "creation "]);
sb.add("if you are ").add("building lots of strings.");
var fullString = sb.toString();
數字
主要就2種，int 和 double, 它們都繼承num類型
數字和字符串之間的轉換
// String -> int
var one = Math.parseInt("1");
assert(one == 1);
// String -> double
var onePointOne = Math.parseDouble("1.1");
assert(onePointOne == 1.1);
// int -> String
var oneAsString = 1.toString();
assert(oneAsString == "1");
// double -> String
var piAsString = 3.14159.toStringAsFixed(2);
assert(piAsString == "3.14");
布爾類型bool，不同于js, 只要不是true, 那么就都是false.
Lists(可以當做數組)
var list = [1,2,3]; //實例化一個list
list.add(4); //添加一個元素4
可以使用for, for...in, foreach()來遍歷一個list.
var list = [1,2,3];
for (final x in list) {
print(x);
}
或者
var list = [1,2,3];
list.forEach((element) => print(element));
Maps（字典類型)
var gifts = { // A map literal
// Keys Values
"first" : "partridge",
"second" : "turtledoves",
"fifth" : "golden rings"};
gifts["third"] = "apple"; //添加一個
使用foreach遍歷
var gifts = {
"first" : "partridge",
"second": "turtledoves",
"fifth" : "golden rings"};
gifts.forEach((k,v) => print('$k : $v'));
getKeys()和getValues()方法
var gifts = {"first": "partridge", "second": "turtledoves"};
var values = gifts.getValues();
//Print partridge and turtledoves, but not necessarily in that order.
values.forEach((v) => print(v));
