The problem

At present, we need to save some user configuration. It can still be read normally after the APP is deleted, so we will use [Key chain].

Key Chain Introduction

When sensitive information (passwords, keys, etc.) needs to be stored in projects, Apple provides a storage mechanism called keychain. A keychain is an encrypted database stored on a hard disk. This may be the reason why the keychain information remains after the App is uninstalled. A keychain is suitable for storing a small amount of data (no more than 1000 bytes or up to megabytes).

The solution

JJKeychain.h

@interface JJKeychain: NSObject @interface JJKeychain: NSObject Then the saved value is converted to NSData. If the value is a user-defined object, it must follow the NSSecureCoding protocol + (BOOL)setValue:(id)value forKey:(NSString *)key; + (BOOL)setValue:(id)value forKey:(NSString *)key forAccessGroup:(nullable NSString *)group; + (id)valueForKey:(NSString *)key; + (id)valueForKey:(NSString *)key forAccessGroup:(nullable NSString *)group; + (BOOL)deleteValueForKey:(NSString *)key; + (BOOL)deleteValueForKey:(NSString *)key forAccessGroup:(nullable NSString *)group; + (NSString *)getBundleSeedIdentifier; @endCopy the code

JJKeychain.m

@implementation JJKeychain + (NSMutableDictionary *)getKeychainQuery:(NSString *)key forAccessGroup:(NSString *)group{ NSMutableDictionary *query = @{(__bridge id)kSecClass : (__bridge id)kSecClassGenericPassword, (__bridge id)kSecAttrService : key, (__bridge id)kSecAttrAccount : key, (__bridge id)kSecAttrAccessible : (__bridge id)kSecAttrAccessibleAfterFirstUnlock }.mutableCopy; if (group ! = nil) { [query setObject:[self getFullAccessGroup:group] forKey:(__bridge id)kSecAttrAccessGroup]; } return query; } + (NSString *)getFullAccessGroup:(NSString *)group { NSString *accessGroup = nil; NSString *bundleSeedIdentifier = [self getBundleSeedIdentifier]; if (bundleSeedIdentifier ! = nil && [group rangeOfString:bundleSeedIdentifier].location == NSNotFound) { accessGroup = [NSString stringWithFormat:@"%@.%@", bundleSeedIdentifier, group]; } return accessGroup; } + (NSString *)getBundleSeedIdentifier { static __strong NSString *bundleSeedIdentifier = nil; if (bundleSeedIdentifier == nil) { @synchronized(self) { if (bundleSeedIdentifier == nil) { NSString *_bundleSeedIdentifier = nil; NSDictionary *query = @{ (__bridge id)kSecClass: (__bridge NSString *)kSecClassGenericPassword, (__bridge id)kSecAttrAccount: @"bundleSeedID", (__bridge id)kSecAttrService: @"", (__bridge id)kSecReturnAttributes: (__bridge id)kCFBooleanTrue }; CFDictionaryRef result = nil; OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef *)&result); if (status == errSecItemNotFound) { status = SecItemAdd((__bridge CFDictionaryRef)query, (CFTypeRef *)&result); } if (status == errSecSuccess) { NSString *accessGroup = [(__bridge NSDictionary *)result objectForKey:(__bridge NSString *)kSecAttrAccessGroup]; NSArray *components = [accessGroup componentsSeparatedByString:@"."]; // NSLog(@"components %@",components); _bundleSeedIdentifier = [[components objectEnumerator] nextObject]; CFRelease(result); } if (_bundleSeedIdentifier ! = nil) { bundleSeedIdentifier = [_bundleSeedIdentifier copy]; } } } } return bundleSeedIdentifier; } + (BOOL)setValue:(id)value forKey:(NSString *)key{ return [self setValue:value forKey:key forAccessGroup:nil]; } + (BOOL)setValue:(id)value forKey:(NSString *)key forAccessGroup:(NSString *)group{ NSMutableDictionary *query = [self  getKeychainQuery:key forAccessGroup:group]; [self deleteValueForKey:key forAccessGroup:group]; NSData *data = nil; @try { data = [NSKeyedArchiver archivedDataWithRootObject:value]; } @catch (NSException *exception) { NSLog(@"archived failure value %@ %@",value,exception); return NO; } [query setObject:data forKey:(__bridge id)kSecValueData]; OSStatus result = SecItemAdd((__bridge CFDictionaryRef)query, NULL); return result == errSecSuccess; } + (BOOL)deleteValueForKey:(NSString *)key{ return [self deleteValueForKey:key forAccessGroup:nil]; } + (BOOL)deleteValueForKey:(NSString *)key forAccessGroup:(NSString *)group{ NSMutableDictionary *query = [self getKeychainQuery:key forAccessGroup:group]; OSStatus result = SecItemDelete((__bridge CFDictionaryRef)query); return result == errSecSuccess; } + (id)valueForKey:(NSString *)key{ return [self valueForKey:key forAccessGroup:nil]; } + (id)valueForKey:(NSString *)key forAccessGroup:(NSString *)group{ id value = nil; NSMutableDictionary *query = [self getKeychainQuery:key forAccessGroup:group]; CFDataRef keyData = NULL; [query setObject:(__bridge id)kCFBooleanTrue forKey:(__bridge id)kSecReturnData]; [query setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit]; if (SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef *)&keyData) == errSecSuccess) { @try { value = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge NSData *)keyData]; } @catch (NSException *e) { NSLog(@"Unarchive of %@ failed: %@", key, e); value = nil; } } if (keyData) { CFRelease(keyData); } return value; } @endCopy the code

Reference: www.jianshu.com/p/354ea1279…