oc 枚举 常量的定义

• 多用const常量类型少用#define预处理指令
• 枚举来表示状态，选项，状态码

typedef NS_ENUM(NSUInteger,NETConnectionState) {
    NETConnectionStateDisconnected,
    NETConnectionStateConnecting = 3,
    NETConnectionStateConnected
};

NETConnectionState netState = NETConnectionStateConnecting;
NSLog(@"netState : %lu",netState); // netState : 3
NSLog(@"NETConnectionStateDisconnected : %lu",(unsigned long)NETConnectionStateDisconnected); // NETConnectionStateDisconnected : 0
NSLog(@"NETConnectionStateConnecting : %lu",(unsigned long)NETConnectionStateConnecting); // NETConnectionStateConnecting : 3
NSLog(@"NETConnectionStateConnected : %lu",(unsigned long)NETConnectionStateConnected); // NETConnectionStateConnected : 4

可以将一些公共常量和枚举放在一个.h文件中

• Const.h 存放一些公共常量枚举文件

NSString * const terminal = @"iPhone";

// 职业
typedef NS_ENUM(NSUInteger,EmployeeType) {
    EmployeeTypeDeveloper,
    EmployeeTypeDesigner,
    EmployeeTypeFinance,
};

// 网络状态
typedef NS_ENUM(NSUInteger,NETConnectionState) {
    NETConnectionStateDisconnected,
    NETConnectionStateConnecting = 3,
    NETConnectionStateConnected
};

• 实现文件

#import <Foundation/Foundation.h>
#import "Const.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        
        NETConnectionState netState = NETConnectionStateConnecting;
        NSLog(@"netState : %lu",netState); // netState : 3
        NSLog(@"NETConnectionStateDisconnected : %lu",(unsigned long)NETConnectionStateDisconnected); // NETConnectionStateDisconnected : 0
        NSLog(@"NETConnectionStateConnecting : %lu",(unsigned long)NETConnectionStateConnecting); // NETConnectionStateConnecting : 3
        NSLog(@"NETConnectionStateConnected : %lu",(unsigned long)NETConnectionStateConnected); // NETConnectionStateConnected : 4
        
        NSLog(@"终端: %@",terminal);
        
        
    }
    return 0;
}