Lesson Set Permissions on an Object

This Tutorial is known to work with hydra-head version 6.4.0.
Please update this wiki to reflect any other versions that have been tested.

Goals

Explanation

Steps

All these steps are on the rails console.

book = Book.new

Step 1: List the current permissions

book.permissions
 => []

Step 2: Grant a variety of permissions all at once

Permissions are basically tracked as an array of Hashes that each specifies

• :name - the user id or group id
• :access - the access type (usually discover, read or edit)
• :type - either group or person

One way to set these is to manually modify the whole array all at once.

book.permissions_attributes = [{:name=>"bob1", :access=>"edit", :type=>'person'}, 
  {:name=>"sally2", :access=>"edit", :type=>'person'}, {:name=>"group1", :access=>"read", :type=>'group'}, 
  {:name=>"group2", :access=>"discover", :type=>'group'}]

Step 3: Use the API methods to inspect the permissions

Getting the whole array of permissions is a bit unwieldy. Modifying it is unwieldy too.

book.permissions
=> [{:name=>"bob1", :access=>"edit", :type=>"person"}, {:name=>"sally2", :access=>"edit", :type=>"person"}, {:name=>"group1", :access=>"read", :type=>"group"}, {:name=>"group2", :access=>"discover", :type=>"group"}] 

To get around this, Hydra provides some methods that let you get directly at the juicy bits.

book.edit_users 
 => ["bob1", "sally2"] 
book.read_users 
 => [] 
book.discover_users 
 => [] 
book.edit_groups 
 => [] 
book.read_groups 
 => ["group1"] 
book.discover_groups 
 => ["group2"] 

Step 4: Use the API methods to modify permissions

book.read_groups 
 => ["group1"] 
book.read_groups = ["group3", "group4", "group5"]
 => ["group3", "group4", "group5"]
book.read_users = ["user3"]
 => ["user3"]

Notice that this removes any group that was not in the array you provided. In other words, it is replacing the previous list of groups with a new definitive list.

Step 5: Use the API set_ methods to modify permissions

If you only want your changes to impact certain groups, use set_read_groups, which takes a second argument that is a list of which groups are eligible to be updated.

Examples of set_read_groups

In this example, no groups are "eligible", so the new group will be added but none of the others will be removed. This would be how you add a group to the list without removing anyone else.

book.read_groups 
 => ["group3", "group4", "group5"]
book.set_read_groups( ["group8"], [])
 => {}
book.read_groups
 => ["group3", "group4", "group5", "group8"]

In this example, groups 4, 5 and 8 are all eligible while group 3 is not, so group3 is left alone while all the others get wiped out because they're not in the list of groups being granted read access.

book.set_read_groups( ["group9"], ["group8", "group4", "group5"])
 => {} 
book.read_groups
 => ["group3", "group9"]

Step 6: Save the Object

Now save the book to Fedora. In the next lesson we will see how the access info is persisted in the rightsMetadata XML datastream.

book.save

Next Step

Go on to Lesson - Reading Hydra rightsMetadata XML or return to the Access Controls with Hydra tutorial.