Create, delete, or modify assets and collections in a photo library by making change requests.
PHCollection instances are immutable objects, you can't make changes to them. To modify the Photos assets or collections these objects represent, use the shared photo library to execute a change block. Inside the change block, create change request objects. Then apply a change block with one of the methods listed in Applying Changes to the Photo Library. The changes you request take effect after Photos runs the change block and calls your completion handler.
Each of the change request classes—
PHCollection—corresponds to an asset or collection class. Use these classes to make the following types of changes:
Creating items. Each change request class provides methods for requesting to create a new item of the corresponding asset or collection class. For example, use the
creation method to create an asset collection.
To reference a newly created request within the change block—for example, to add a new asset to a collection—use the
PHObject object provided by the change request. After the change block completes, use the placeholder object’s
local property to fetch the created object.
Deleting items. Each change request class provides methods for requesting to delete one or more items of the corresponding asset or collection class. For example, use the
delete method to delete collection lists.
Modifying items. You modify an existing asset or collection by creating a change request from a
PHCollection object representing it. For example, the
change method creates a change request you can use for modifying an asset.
After creating a change request, use its properties and instance methods to modify the corresponding features of the asset or collection it represents. For example, to set an asset’s
favorite property, set the
favorite property of a change request created from that asset. To add to an asset collection, call the
add method on an asset collection change request.
Create an Asset for an Album
Use a change block to combine several changes to the photo library into a single atomic update. The following code uses a change block to create an asset from an image and add that asset to an album.
For each call to the
perform method, Photos shows an alert asking the user for permission to edit the contents of the photo library. If your app needs to submit several changes at once, combine them into a single change block.
For example, to add several new images in one batch, extend the code to create multiple
PHAsset objects using the
creation method. To edit the content of multiple existing photos, create multiple
PHAsset objects and set the
content property on each to an independent
You can modify and delete assets in a similar way.