OC枚舉值到字符串轉(zhuǎn)換
緣起
Objective-C中經(jīng)常需要將枚舉轉(zhuǎn)換成對(duì)應(yīng)的字符串類(lèi)型。平時(shí)一般用if或switch語(yǔ)句返回枚舉值對(duì)應(yīng)的字符串涛碑，高級(jí)一點(diǎn)的呢就使用字典做映射变擒，如：
typedef NS_ENUM(NSUInteger, RAPDirection) {
RAPDirectionUp,
RAPDirectionDown,
RAPDirectionLeft,
RAPDirectionRight
};
- (NSString *)stringForRAPDirection:(RAPDirection)type {
static NSDictionary *map = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
map = @{
@(RAPDirectionUp): @"上",
@(RAPDirectionDown): @"下",
@(RAPDirectionLeft): @"左",
@(RAPDirectionRight): @"右",
};
});
return map[@(type)] ?: @"unknown";
}
相比之下, Swfit要簡(jiǎn)單的多随静。Swift枚舉類(lèi)型引入了Raw Value的概念囚企，每個(gè)枚舉case的Raw Value可以是其case name畜伐。假設(shè)有case up馍惹，則up.rawValue = "上"。
那有沒(méi)有更簡(jiǎn)單的一步到位的方法，在定義時(shí)候就榜單相應(yīng)的字符串呢万矾？看到一篇文章OC枚舉值到字符串轉(zhuǎn)換, 作者用宏替換實(shí)現(xiàn)了將枚舉值映射為對(duì)應(yīng)的字符串悼吱，如枚舉值RAPDirectionUp映射成@"RAPDirectionUp". 在此基礎(chǔ)上，我增加了枚舉值映射成自定義文字的功能良狈，如RAPDirectionUp映射成@"上"后添。
安裝
==============
CocoaPods
- 在 Podfile 中添加
pod 'EnumStringConvertible'。 - 執(zhí)行
pod install或pod update薪丁。 - 導(dǎo)入 <EnumStringConvertible/EnumMarcos.h>遇西。
A. 使用
這套宏的用法分為兩步：
A.1 在.h文件中定義枚舉，聲明反射函數(shù)
// M1
#define RAP_DIRECTION(XX) \
XX(RAPDirectionUp, ) \
XX(RAPDirectionDown, , 下) \
XX(RAPDirectionLeft, = 50, 左) \
XX(RAPDirectionRight, = 100, 右) \
// M2
DECLARE_ENUM(RAPDirection, RAP_DIRECTION)
M1生成多個(gè)枚舉case严嗜。枚舉case的定義格式為XX(name, assign)粱檀，name即case name；assign即對(duì)應(yīng)整數(shù)值漫玄，格式必須為
= Integer茄蚯，不填表示使用默認(rèn)值；第三個(gè)參數(shù)為要映射的描述睦优，不填則返回name第队。-
M2定義枚舉，聲明反射函數(shù)。反射函數(shù)的有三個(gè)：
- 根據(jù)case獲取case name：NameFromRAPDirection(RAPDirection value);
- 根據(jù)case獲取case 描述： DescriptionFromRAPDirection(RAPDirection value);
- 根據(jù)case name獲取case：RAPDirectionFromNSString(NSString *string);
A.2 在.m文件中實(shí)現(xiàn)反射函數(shù)
DEFINE_ENUM(RAPDirection, RAP_DIRECTION)
- RAPDirection和RAP_DIRECTION要與.h中的宏對(duì)應(yīng)薪贫。RAPDirection是枚舉類(lèi)型名稱(chēng)驹尼，RAP_DIRECTION是宏，展開(kāi)后變成多個(gè)枚舉case尸执。
A.3 函數(shù)調(diào)用
嘗試使用：
NSString *str2 = DescriptionFromRAPDirection(RAPDirectionUp);
NSLog(@"RAPDirectionUp has case desc: %@", str2);
NSString *str31 = NameFromRAPDirection(RAPDirectionLeft);
NSLog(@"RAPDirectionLeft has case name: %@", str31);
NSString *str32 = DescriptionFromRAPDirection(RAPDirectionLeft);
NSLog(@"RAPDirectionLeft has case desc: %@", str32);
RAPDirection dir = RAPDirectionFromNSString(@"RAPDirectionRight");
NSLog(@"RAPDirectionRight has case value: %zd", dir);
輸出結(jié)果：
RAPDirectionUp has case desc: RAPDirectionUp
RAPDirectionLeft has case name: RAPDirectionLeft
RAPDirectionLeft has case desc: 左
RAPDirectionRight has case value: 100
