IOS开发入门之iOS枚举讲解-职坐标

IOS开发入门之iOS枚举讲解

安安 2017-09-14 来源：网络阅读 864 评论 0

摘要：本篇IOS开发入门文章将为大家讲解iOS枚举讲解，看完这篇文章会让你对IOS编程的知识点有更加清晰的理解和运用。

本篇IOS开发入门文章将为大家讲解iOS枚举讲解，看完这篇文章会让你对IOS编程的知识点有更加清晰的理解和运用。

枚举增强程序的可读性，用法上还是需要注意的

1.C语言的写法

enum XMPPReconnectFlags

{

kShouldReconnect = 1 << 0, // If set, disconnection was accidental, and autoReconnect may be used

kMultipleChanges = 1 << 1, // If set, there have been reachability changes during a connection attempt

kManuallyStarted = 1 << 2, // If set, we were started manually via manualStart method

kQueryingDelegates = 1 << 3, // If set, we are awaiting response(s) from the delegate(s)

};

或者是

typedef enum XMPPReconnectFlags

{

kShouldReconnect = 1 << 0, // If set, disconnection was accidental, and autoReconnect may be used

kMultipleChanges = 1 << 1, // If set, there have been reachability changes during a connection attempt

kManuallyStarted = 1 << 2, // If set, we were started manually via manualStart method

kQueryingDelegates = 1 << 3, // If set, we are awaiting response(s) from the delegate(s)

}XMPPReconnectFlags;//此处的XMPPReconnectFlags为别名

2.OC的写法

typedef NS_ENUM(NSInteger, XMPPMessageBodyType) {

XMPPMessageBodyTypeText = 1, //文本

XMPPMessageBodyTypeImage, //图片

XMPPMessageBodyTypeSound, //语音

XMPPMessageBodyTypeMap, //地理信息（文本）

XMPPMessageBodyTypeNotification, //通知

XMPPMessageBodyTypeCustom, //自定义

XMPPMessageBodyTypeVideo, //视频

XMPPMessageBodyTypeExpression, //表情

};

第一个枚举值只要NSInteger类型，后面的依次累加，中间再重新赋值，后面的会从赋值处重新累加

3.NS_ENUM和NS_OPTIONS

NS_ENUM和NS_OPTIONS本质是一样的，仅仅从字面上来区分其用途。NS_ENUM是通用情况，NS_OPTIONS一般用来定义具有位移操作或特点的情况

typedef NS_OPTIONS(NSInteger, ShareViewItemType) {

ShareViewItemTypeWX = 1,

ShareViewItemTypeWXFC = 1 << 0,

ShareViewItemTypeQQ= 1 << 1,

ShareViewItemTypeWB= 1 << 1,

ShareViewItemTypeReport= 1 << 3,

ShareViewItemTypeBarrage = 1 << 4,

ShareViewItemTypeAll = 1 << 5,

};

如果多选枚举，那么需要这样判断

+ (instancetype)shareViewWithDic:(NSDictionary*)dic shareViewItemType:(ShareViewItemType)shareViewItemType;

{

if (shareViewItemType == (ShareViewItemTypeWX|ShareViewItemTypeWXFC)) {

// code

}

4.官方的全选枚举

UIControl的枚举

typedef NS_OPTIONS(NSUInteger, UIControlEvents) {

UIControlEventTouchDown = 1 << 0, // on all touch downs

UIControlEventTouchDownRepeat = 1 << 1, // on multiple touchdowns (tap count > 1)

UIControlEventTouchDragInside = 1 << 2,

UIControlEventTouchDragOutside = 1 << 3,

UIControlEventTouchDragEnter = 1 << 4,

UIControlEventTouchDragExit = 1 << 5,

UIControlEventTouchUpInside = 1 << 6,

UIControlEventTouchUpOutside = 1 << 7,

UIControlEventTouchCancel = 1 << 8,

UIControlEventValueChanged = 1 << 12, // sliders, etc.

UIControlEventPrimaryActionTriggered NS_ENUM_AVAILABLE_IOS(9_0) = 1 << 13, // semantic action: for buttons, etc.

UIControlEventEditingDidBegin = 1 << 16, // UITextField

UIControlEventEditingChanged = 1 << 17,

UIControlEventEditingDidEnd = 1 << 18,

UIControlEventEditingDidEndOnExit = 1 << 19, // 'return key' ending editing

UIControlEventAllTouchEvents = 0x00000FFF, // for touch events

UIControlEventAllEditingEvents = 0x000F0000, // for UITextField

UIControlEventApplicationReserved = 0x0F000000, // range available for application use

UIControlEventSystemReserved = 0xF0000000, // range reserved for internal framework use

UIControlEventAllEvents = 0xFFFFFFFF

};

最后一个 UIControlEventAllEvents赋值为0xFFFFFFFF，意为全选，实际工程使用没有问题，很方便，但是在
Archive的时候会报错

IOS开发入门之iOS枚举讲解

这个地方需要这样改

typedef NS_OPTIONS(NSUInteger, ShareViewItemType) {

ShareViewItemTypeWX = 1,

ShareViewItemTypeWXFC = 1 << 0,

ShareViewItemTypeQQ= 1 << 1,

ShareViewItemTypeWB= 1 << 1,

ShareViewItemTypeReport= 1 << 3,

ShareViewItemTypeBarrage = 1 << 4,

ShareViewItemTypeAll = 0xFFFFFFFF,

};

你可以这样判断条件

+ (instancetype)shareViewWithDic:(NSDictionary*)dic shareViewItemType:(ShareViewItemType)shareViewItemType;

{

// 入参shareViewItemType为ShareViewItemTypeAll

if (shareViewItemType & ShareViewItemTypeBarrage) {

// code

}

5.使用层面的理解

在这里首先讲如何简单的使用, 仅仅是使用层面(有理解错误的地方帮忙纠正), 然后我们在去理解位运算符! 在下面的图中我们可以看见枚举值中有<<(位运算符:左移):

IOS开发入门之iOS枚举讲解

如果我们在枚举值中看见<<那我们就可以通过|(位运算符:或)进行组合使用如下代码为例:

//随便添加一个UITextField

UITextField *field = [UITextField new];

//Begin,Changed,DidEnd都能触发UITextField的事件

[field addTarget:self action:@selector(textFieldDidChanged) forControlEvents: UIControlEventEditingDidBegin |

UIControlEventValueChanged |

UIControlEventEditingDidEnd

];

[self.view addSubview:field];

如下图枚举值中没有<<,这就是普通的NSInteger类型的枚举, 所以不能组合使用:

IOS开发入门之iOS枚举讲解

那苹果官方是怎么知道我们多个条件组合使用了呢? 答案是通过&(位运算符:与)进行判断的:

//controlEvents是组合使用后的一个值

NSUInteger controlEvents = UIControlEventEditingDidBegin | UIControlEventValueChanged | UIControlEventEditingDidEnd;

/**

//通过 & 来判断是否包含:

UIControlEventEditingDidBegin,

UIControlEventValueChanged,

UIControlEventEditingDidEnd

if (controlEvents & UIControlEventEditingDidBegin) {

NSLog(@"UIControlEventEditingDidBegin");

}else if (controlEvents & UIControlEventValueChanged) {

NSLog(@"UIControlEventValueChanged");

}else if (controlEvents & UIControlEventEditingDidEnd) {

NSLog(@"UIControlEventEditingDidEnd");

}

那么我们接下来看看使用过程中牵扯到的位运算符, 我们会在下面举个例子!

6.理解位运算符

首先我们有一个枚举, 下面代码2种写法我们暂时先不用管,等位运算符讲完我们会讨论枚举的宏使用:

//typedef NS_OPTIONS(NSInteger, myTests) {

// nameA = 1 << 0,

// nameB = 1 << 1,

// nameC = 1 << 2,

// nameD = 1 << 3,

//};

typedef enum {

nameA = 1 << 0,

nameB = 1 << 1,

nameC = 1 << 2,

nameD = 1 << 3,

}myTests;

/**

nameA = 1 << 0 :值为1(2的0次方)

nameB = 1 << 1 :值为2(2的1次方)

nameC = 1 << 2 :值为4(2的2次方)

nameD = 1 << 3 :值为8(2的3次方)

通过&进行判断我们来看看输出结果如下图:

IOS开发入门之iOS枚举讲解

我们得到NSInteger value = nameA | nameB;的组合的值, 判断结果是:1是nameA的值, 2是nameB的值, nameC与nameD没有组合使用所以值为0,最后我们知道如果value & nameC为0说明value不包含nameC 相反则包含!

还有一点就是value & nameA就是nameA的值为1, value & nameB就是nameB的值为2

· <<(左移):a << b就表示把a转为二进制后左移b位（在后面添b个0）

· |(或):只要有一个为1, 结果就是1

· &(与):只要有二个为1, 结果才是1

我们已经知道nameA = 1, nameB = 2, nameC = 4, nameD = 8下面来通过二进制来解释:

NSInteger value = nameA | nameB | nameC | nameD;

转成二进制:

nameA: 0 0 0 1

nameB: 0 0 1 0

nameC: 0 1 0 0

nameD: 1 0 0 0

----------------

value: 1 1 1 1

上面是使用 | 得出value的值为1111(|的意思是有一个为1结果就为1)

下面是使用 & 判断输出的值(&的意思就是有二个为1结果才为1)

value: 1 1 1 1 value: 1 1 1 1

& &

nameA: 0 0 0 1 nameB: 0 0 1 0

---------------- ----------------

结果值: 0 0 0 1 结果值: 0 0 1 0

我就写2个例子:0001就是nameA的值, 0010就是nameB的值

相信大家已经明白其中的道理了, 接下来我们来看看枚举的宏, 为了更好阅读也可以看下面的截图:

IOS开发入门之iOS枚举讲解

7.枚举的宏(NS_ENUM与NS_OPTIONS)

NS_ENUM和NS_OPTIONS宏提供了一个简洁、定义枚举和C语言选项的简单方法。

The NS_ENUM and NS_OPTIONS macros provide a concise, simple way of defining enumerations and options in C-based languages. These macros improve code completion in Xcode and explicitly specify the type and size of your enumerations and options. Additionally, this syntax declares enums in a way that is evaluated correctly by older compilers, and by newer ones that can interpret the underlying type information.

这是最初的使用方法:

enum {

UITableViewCellStyleDefault,

UITableViewCellStyleValue1,

UITableViewCellStyleValue2,

UITableViewCellStyleSubtitle

};

typedef NSInteger UITableViewCellStyle;

--------------------------------------------------

enum {

UIViewAutoresizingNone = 0,

UIViewAutoresizingFlexibleLeftMargin = 1 << 0,