ios开发中常用的几种辅助方法

//1.Keychain本地长期键值存储
//删除
+(void)deleteStringForKey:(NSString *)aKey
{NSMutableDictionary *query = [NSMutableDictionary dictionary];[query setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge  id)kSecClass];[query setObject:(id)aKey forKey:(__bridge id)kSecAttrAccount];OSStatus status = SecItemDelete((__bridge CFDictionaryRef)query);if (status != noErr) {// NSLog(@"[KeychainAccessor]>>> SecItemDelete result in error:(%d)", (int)status);}
}
//存储
+ (void)setString:(NSString *)aString forKey:(NSString *)aKey
{NSData *savingData = [aString dataUsingEncoding:NSUTF8StringEncoding];NSMutableDictionary *attributes = [NSMutableDictionary dictionary];[attributes setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];[attributes setObject:(id)aKey forKey:(__bridge id)kSecAttrAccount];[attributes setObject:savingData forKey:(__bridge id)kSecValueData];OSStatus status = SecItemAdd((__bridge CFDictionaryRef)attributes, NULL);if ((int)status==-25299) {//  NSLog(@"delete old data add new data");[self deleteStringForKey:aKey];SecItemAdd((__bridge CFDictionaryRef)attributes, NULL);}if (status != noErr) {//  NSLog(@"[KeychainAccessor]>>> SecItemAdd result in error:(%d)",(int)status);}
}
//查询
+ (NSString *)stringForKey:(NSString *)aKey {NSMutableDictionary *query = [NSMutableDictionary dictionary];[query setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge  id)kSecClass];[query setObject:(id)aKey forKey:(__bridge id)kSecAttrAccount];[query setObject:(__bridge id)kCFBooleanTrue forKey:(__bridge id)kSecReturnData];[query setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];CFDataRef result = nil;OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef*)&result);if (status != noErr) {if (status == errSecItemNotFound) {//NSLog(@"[KeychainAccessor]>>> SecItemCopyMatching result NOT-FOUND.");} else {//NSLog(@"[KeychainAccessor]>>> SecItemCopyMatching result in error:(%d)", (int)status);}return @"";}NSData *theValue = [(__bridge NSData*)result copy];return [[NSString alloc] initWithData:theValue encoding:NSUTF8StringEncoding];
}//2.压缩图片到指定尺寸大小
+ (UIImage *)compressOriginalImage:(UIImage *)image toSize:(CGSize)size{UIImage *resultImage = image;UIGraphicsBeginImageContext(size);[resultImage drawInRect:CGRectMake(0, 0, size.width, size.height)];UIGraphicsEndImageContext();return resultImage;
}//3.压缩图片到指定文件大小
+ (NSData *)compressOriginalImage:(UIImage *)image toMaxDataSizeKBytes:(CGFloat)size{NSData *data = UIImageJPEGRepresentation(image, 1.0);CGFloat dataKBytes = data.length/1000.0;CGFloat maxQuality = 0.9f;CGFloat lastData = dataKBytes;while (dataKBytes > size && maxQuality > 0.01f) {maxQuality = maxQuality - 0.01f;data = UIImageJPEGRepresentation(image, maxQuality);dataKBytes = data.length/1000.0;if (lastData == dataKBytes) {break;}else{lastData = dataKBytes;}}return data;
}//全屏截图
+ (UIImage *)shotScreen{UIWindow *window = [UIApplication sharedApplication].keyWindow;UIGraphicsBeginImageContext(window.bounds.size);[window.layer renderInContext:UIGraphicsGetCurrentContext()];UIImage *image = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();return image;
}

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