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，让用户从他们的图库中拍照来做事情。我正在使用X代码，并且我在'didFinishLaunchingWithOptions'下面有了这段代码，但不断收到'未声明的标识符'错误。该怎么办？

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

太晚了一个答案，但你需要定义库

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

或更好地使用一个类的方法，如果你打算重用库更多查询

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