获取到UUID后，如果用NSUserDefaults存储，当程序被卸载后重装时，再获得的UUID和之前就不同了。使用keychain存储可以保证程序卸载重装时，UUID不变。但当刷机后，UUID还是会改变的。但这仍是目前为止最佳的解决办法了，如果有更好的解决办法，欢迎留言。
1.新建一个工程，看一下自己的Bundle Id.这个Bundle Id 要和你用真机测试时的证书上面的Bundle Id相匹配。
2.Target - Capabilities - Keychain Sharing 改为ON
然后，在左侧的目录会自动生成Entitlements文件，不用自己创建了。
注意：Bundle Identifier、Keychain Sharing的Keychain Groups、Entitlements文件的Keychain Access Groups的第一个元素，它们要保持上图所示的一致性。
设置好了以后可以运行下程序，没问题可以进行下一步。
3.接下来，就是UUID类和keychain类了（我也是从网上搬运来的，作者看到勿喷。。。）
UUID.h
#import <Foundation/Foundation.h>
@interface UUID : NSObject
+(NSString *)getUUID;
@end
UUID.m
#import "UUID.h"
#import "KeyChainStore.h"
@implementation UUID
+(NSString *)getUUID
{
NSString * strUUID = (NSString *)[KeyChainStore load:@"com.company.app.usernamepassword"];
//首次执行该方法时，uuid为空
if ([strUUID isEqualToString:@""] || !strUUID)
{
//生成一个uuid的方法
CFUUIDRef uuidRef = CFUUIDCreate(kCFAllocatorDefault);
strUUID = (NSString *)CFBridgingRelease(CFUUIDCreateString (kCFAllocatorDefault,uuidRef));
//将该uuid保存到keychain
[KeyChainStore save:KEY_USERNAME_PASSWORD data:strUUID];
}
return strUUID;
}
@end
KeyChainStore.h
#import <Foundation/Foundation.h>
@interface KeyChainStore : NSObject
+ (void)save:(NSString *)service data:(id)data;
+ (id)load:(NSString *)service;
+ (void)deleteKeyData:(NSString *)service;
@end
KeyChainStore.m
#import "KeyChainStore.h"
@implementation KeyChainStore
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
return [NSMutableDictionary dictionaryWithObjectsAndKeys:
(id)kSecClassGenericPassword,(id)kSecClass,
service, (id)kSecAttrService,
service, (id)kSecAttrAccount,
(id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible,
nil];
}
+ (void)save:(NSString *)service data:(id)data {
//Get search dictionary
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Delete old item before add new item
SecItemDelete((CFDictionaryRef)keychainQuery);
//Add new object to search dictionary(Attention:the data format)
[keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];
//Add item to keychain with the search dictionary
SecItemAdd((CFDictionaryRef)keychainQuery, NULL);
}
+ (id)load:(NSString *)service {
id ret = nil;
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Configure the search setting
//Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue
[keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
[keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
CFDataRef keyData = NULL;
if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {
@try {
ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge NSData *)keyData];
} @catch (NSException *e) {
NSLog(@"Unarchive of %@ failed: %@", service, e);
} @finally {
}
}
if (keyData)
CFRelease(keyData);
return ret;
}
+ (void)deleteKeyData:(NSString *)service {
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
SecItemDelete((CFDictionaryRef)keychainQuery);
}
@end
将这两个类添加到工程中
4.新建一个pch文件，给pch文件添加的内容如下：
#define KEY_USERNAME_PASSWORD @"com.company.app.usernamepassword"
#define KEY_USERNAME @"com.company.app.username"
#define KEY_PASSWORD @"com.company.app.password"
添加pch文件方法可参照：创建.pch文件 - 简书
5.最后，在viewController里面添加头文件，调用
NSString * uuid= [UUID getUUID];
NSLog(@"UUID = %@",uuid);
打印出来的是这个样子：UUID = F6574AFA-6B6E-4699-A889-799944AA3861
然后呢就可以多试几次，看看各种情况下，会不会改变
PS：重装系统没有试过，但是卸载APP重装后，UUID不会变，要是有人测试过重装系统后，一定将结果告诉我喔！
