flutter语言篇三

最新推荐文章于 2024-10-17 23:13:43 发布

weixin_33827590

最新推荐文章于 2024-10-17 23:13:43 发布

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CC 4.0 BY-SA版权

文章标签：移动开发

原文链接：https://juejin.im/post/5cdd111c6fb9a0323f68c503

特殊操作符

1. as,is,is!

as 类型转换

(emp as Person).firstName = 'Bob';
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is 类型判断

if (emp is Person) {
  // Type check
  emp.firstName = 'Bob';
}
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2. 赋值操作符 ??=

b值为null，则赋值为value

// Assign value to b if b is null; otherwise, b stays the same
b ??= value;
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3. 条件运算符

condition为true，则值为expr1;否则为expr2

condition ? expr1 : expr2

var visibility = isPublic ? 'public' : 'private';
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expr1不为空，则值为expr1;否则为expr2

expr1 ?? expr2

String playerName(String name) => name ?? 'Guest';
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4. switch-case

case 后有操作语句，而无break报错

var command = 'OPEN';
switch (command) {
  case 'OPEN':
    executeOpen();
    // ERROR: Missing break

  case 'CLOSED':
    executeClosed();
    break;
}
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case后无操作语句，可缺少break

var command = 'CLOSED';
switch (command) {
  case 'CLOSED': // Empty case falls through.
  case 'NOW_CLOSED':
    // Runs for both CLOSED and NOW_CLOSED.
    executeNowClosed();
    break;
}
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case后有操作语句，希望继承执行，可使用continue

var command = 'CLOSED';
switch (command) {
  case 'CLOSED':
    executeClosed();
    continue nowClosed;
  // Continues executing at the nowClosed label.

  nowClosed:
  case 'NOW_CLOSED':
    // Runs for both CLOSED and NOW_CLOSED.
    executeNowClosed();
    break;
}
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