Category method to get permission before using ALAssetsLibrary like ACAccountStore, EKEventStore.

ALAssetsLibrary+CSNAdditions.h

//
//  ALAssetsLibrary+CSNAdditions.h
//
// The MIT License (MIT)
// 
// Copyright (c) 2014 griffin-stewie
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#import <AssetsLibrary/AssetsLibrary.h>

@interface ALAssetsLibrary (CSNAdditions)

+ (void)csn_requestAccessToAssetsLibraryWithCompletionBlock:(void(^)(BOOL granted, NSError *error))block;

@end

ALAssetsLibrary+CSNAdditions.m

//
//  ALAssetsLibrary+CSNAdditions.m
//
// The MIT License (MIT)
// 
// Copyright (c) 2014 griffin-stewie
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#import "ALAssetsLibrary+CSNAdditions.h"

@implementation ALAssetsLibrary (CSNAdditions)

+ (void)csn_requestAccessToAssetsLibraryWithCompletionBlock:(void(^)(BOOL granted, NSError *error))block
{
	void(^callBlock)(BOOL granted, NSError *error) = ^(BOOL granted, NSError *error) {
		if (block) {
			block(granted, error);
		}
	};
    
	if ([ALAssetsLibrary authorizationStatus] == ALAuthorizationStatusAuthorized) {
		callBlock(YES, nil);
		return;
	}
    
	ALAssetsLibrary *lib = [[ALAssetsLibrary alloc] init];
	[lib enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
		/// avoid duplication call
		if (group || !*stop) {
			*stop = YES;
			callBlock(YES, nil);
		}
	} failureBlock:^(NSError *error) {
		callBlock(NO, error);
	}];
}

@end