Dart基础语言学习—常量

Dart基础语言学习—常量

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类型声明可以省略

final String a = 'final-string-dart';
final a = 'final-a-dart'

const String a = 'const-string-a';
const a = 'const-a';

初始后不能再赋值

final a = 'final-a';
a = 'abc';

const a = 'const-a';
a = 'abc';

不能和 var 同时使用

final var a = 'final-var-a';
const var a = 'const-var-a';

const 赋值 申明可省略

const List ls = const [11, 22, 33];
const List ls = [11, 22, 33];

区别

需要确定的值

final dt = DateTime.now();

const dt = const DateTime.now();

不可变性可传递

final List ls = [11, 22, 33];
ls[1] = 44;

const List ls = [11, 22, 33];
ls[1] = 44;

内存中重复创建

final a1 = [11 , 22];
final a2 = [11 , 22];
print(identical(a1, a2));

const a1 = [11 , 22];
const a2 = [11 , 22];
print(identical(a1, a2));

PDF文档整理：

Dart基础语言学习-上篇.pdf