iOS小技巧-使用UUID+keychain替代udid方案

众所周知，苹果对用户的隐私越来越重视，导致app要获取用户的信息越来越少，参考网上的资料，写这篇文章作为日后的参考。

首先是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文件

#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           

之后是写一个工具类UUID.h文件

#import <Foundation/Foundation.h>

@interface UUID : NSObject

+(NSString *)getUUID;

@end           

最后是UUID.m文件

#import "UUID.h"
#import "KeyChainStore.h"

@implementation UUID

+(NSString *)getUUID
{
    //获取项目的bundle ID
    NSString *bundleId = [[NSBundle mainBundle] bundleIdentifier];
    //根据bundle ID拼接一个自定义的key用来作为keychain里面的唯一标示
    //NSString *keyUUid = [NSString stringWithFormat:@"%@.uuid",bundleId];
    //将bundle ID作为唯一key在keychain里面获取保存的uuid
    NSString * strUUID = (NSString *)[KeyChainStore load:bundleId];
    
    //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:bundleId data:strUUID];
        
    }
    return strUUID;
}

@end           

这样就可以生成一个固定的类似udid的字符串，即时app卸载后再重新安装，也能获取到一个唯一的固定字符串。