如何在启动时要求访问照片库？

Question

我正在构建一个应用程序，让用户从他们的库中拍照来做事情。我使用的是X代码，而且我的代码是在＆f; finishLaunchingWithOptions＆＃39;但不断获得一个未声明的标识符＆＃39;错误。怎么办？

ALAssetsLibraryGroupsEnumerationResultsBlock assetGroupEnumerator =
^(ALAssetsGroup *assetGroup, BOOL *stop) {
    if (assetGroup != nil) {
        // do somthing
     }
};

ALAssetsLibraryAccessFailureBlock assetFailureBlock = ^(NSError *error) {
    LogError(@"Error enumerating photos: %@",[error description]);

};

NSUInteger groupTypes = ALAssetsGroupAll;

[library enumerateGroupsWithTypes:groupTypes usingBlock:assetGroupEnumerator failureBlock:assetFailureBlock];

Answer 1

答案太迟了但你需要定义库

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

或更好地使用类方法，如果您要重用该库以进行更多查询

+ (ALAssetsLibrary *)defaultAssetsLibrary
{
    static dispatch_once_t pred = 0;
    static ALAssetsLibrary *library = nil;
    dispatch_once(&pred, ^{
        library = [[ALAssetsLibrary alloc] init];
    });
    return library;
}