Flutter 枚举总结：枚举值 enum 和 int/name 互相转化

一、需求来源

工作中偶尔会用到枚举值和 int 的互相转化，今天总结一下；

二、搞清楚 Flutter 枚举属性和方法

三、实现需求（以 PageView 滚动方式为例）

枚举值转 int：在当前索引值后加 .index 即可（默认从 0 开始）；

int 转枚举值：需要扩展枚举方法实现，实现如下；

定义枚举 PageViewScrollType

/// PageView 滚动方式
enum PageViewScrollType {
  /// 整屏滑动
  full,
  /// 拖拽滑动
  drag,
  /// 禁用滑动
  none,
}

extension PageViewScrollType_IntExt on int{
  /// int 转枚举
  PageViewScrollType? toPageViewScrollType([bool isClamp = true]){
    final allCases = PageViewScrollType.values;
    if (!isClamp) {
      if (this < 0 || this > allCases.length - 1) {
        return null;
      }
      return allCases[this];
    }
    final index = this.clamp(0, allCases.length - 1);
    return allCases[index];
  }

  /// int 转枚举
  PageViewScrollType get pageViewScrollType{
    final allCases = PageViewScrollType.values;
    // final index = this.clamp(0, allCases.length - 1);
    // return allCases[index];
    return this.toPageViewScrollType(true) ?? allCases.first;
  }

}

EnumExt - 枚举通用扩展

//
//  EnumExt.dart
//  flutter_templet_project
//
//  Created by shang on 2024/7/10 09:47.
//  Copyright © 2024/7/10 shang. All rights reserved.
//

import 'package:flutter/cupertino.dart';

/// 可空 name 匹配
extension EnumExt<T extends Enum> on Iterable<T> {
  /// Finds the enum value in this list with name [name].
  T? byNullableName(String? name) {
    if (name == null) {
      return null;
    }
    try {
      return byName(name);
    } catch (e) {
      debugPrint("❌ $e");
    }
    return null;
  }

  /// Finds the enum value in this list with test.
  T? by(bool Function(T e) test) {
    for (final e in this) {
      if (test(e)) {
        return e;
      }
    }
    return null;
  }
}

extension EnumStringExt<T extends Enum> on String? {
  /// 字符串转枚举
  /// values - 枚举数组
  T? enumOf(Iterable<T> values) {
    return values.byNullableName(this);
  }
}

最后

如此就实现了 枚举值和 int的互相转化，打印如下：

print("枚举值索引: ${PageViewScrollType.full.index}");

print("枚举集合: ${PageViewScrollType.values}");
print("int 转枚举: ${0.toPageViewScrollType()}");


String? name = ...;
/// 通过字符串枚举值 name 获取 PageViewScrollType
print("枚举值字符串: ${PageViewScrollType.values.byNullableName(name)}");
print("枚举值字符串: ${name?.enumOf(ActivityTypeNew.values)}");

/// 通过 int 获取 PageViewScrollType
print("枚举值字符串: ${PageViewScrollType.values.by((e) => e.index == 2);}");

//枚举值索引: 0

//枚举值字符串: PageViewScrollType.drag

//枚举集合: [ PageViewScrollType.full, PageViewScrollType.drag, PageViewScrollType.none ]

//int 转枚举: PageViewScrollType.full