My Object has many transactions which belong to a type, whcich then belong to a group. I would like to pull all the transactions from my Object which are in a specific group, say blue.
Been trying to do this using both SQL and Activerecord and have failed in both endeavors.
I can get this procedure to print out the quality by which I then want to sort by:
object.transactions.map { |to| "#{to.transaction_type.transaction_group.name}" }
And here is a sample of what i have been running, but oviously dosen't work. Haven't managed to find a way to
id = Group.find_by_name("name")
object.transactions.where(transaction_type.group_id == id)
Can you do something like:
id = Group.find_by_name("name")
object.transactions.
joins(:type).
where("types.group_id" => id)
Related
After I loaded a List of tasks with a taskQuery
taskService.createTaskQuery()
.processDefinitionKey(PROCESSKEY)
.taskCandidateGroupIn(list).initializeFormKeys().list()
What is the best way to find out the candidate group of every task?
I want to display it in a JSF view, but the class Task has no corresponding field.
You can get a task's identity links using the task service. Among other relations, the candidate group relation is expressed as an identity link. The following code filters a task's identity links for those that represent candidate groups:
List<IdentityLink> identityLinks = taskService.getIdentityLinksForTask(task.getId());
for (IdentityLink identityLink : identityLinks) {
String type = identityLink.getType();
/* type corresponds to the constants defined in IdentityLinkType.
"candidate" identitifies a candidate relation */
String groupId = identityLink.getGroupId();
if (IdentityLinkType.CANDIDATE.equals(type) && groupId != null) {
// we have found a candidate group; do something
}
}
The best approach is to write a custom query that gives you all task information the way you need them with on select. You do not want to start looping over result lists and sending one or more query per item, especially not in a high performance application as your task list.
Check the custom query documentation for details.
Only select task which have a candidate groups.
List<Task> candidateGroupList = taskService.createTaskQuery().withCandidateGroups().list();
A user can create groups
A group had to have created by a user
A user can belong to multiple groups
A group can have multiple users
I have something like the following:
Parse.Cloud.afterSave('Group', function(request) {
var creator = request.user;
var group = request.object;
var wasGroupCreated = group.existed;
if(wasGroupCreated) {
var hasCreatedRelation = creator.relation('hasCreated');
hasCreatedRelation.add(group);
var isAMemberOfRelation = creator.relation('isMemberOf');
isAMemberOfRelation.add(group);
creator.save();
}
});
Now when I GET user/me with include=isMemberOf,hasCreated, it returns me the user object but with the following:
hasCreated: {
__type: "Relation"
className: "Group"
},
isMemberOf: {
__type: "Relation"
className: "Group"
}
I'd like to have the group objects included in say, 'hasCreated' and 'isMemberOf' arrays. How do I pull that using the REST API?
More in general though, am I approaching this the right way? Thoughts? Help is much appreciated!
First off, existed is a function that returns true or false (in your case the wasGroupCreated variable is always going to be a reference to the function and will tis always evaluate to true). It probably isn't going to return what you expect anyway if you were using it correctly.
I think what you want is the isNew() function, though I would test if this works in the Parse.Cloud.afterSave() method as I haven't tried it there.
As for the second part of your question, you seem to want to use your Relations like Arrays. If you used an array instead (and the size was small enough), then you could just include the Group objects in the query (add include parameter set to isMemberOf for example in your REST query).
If you do want to stick to Relations, realise that you'll need to read up more in the documentation. In particular you'll need to query the Group object using a where expression that has a $relatedTo pointer for the user. To query in this manner, you will probably need a members property on the Group that is a relation to Users.
Something like this in your REST query might work (replace the objectId with the right User of course):
where={"$relatedTo":{"object":{"__type":"Pointer","className":"_User","objectId":"8TOXdXf3tz"},"key":"members"}}
I have a object Ob with several fields f1,..,fn (of different types).
Now a list of object is shown in a GridView and I need to implement the sorting method.
The real problem is:
how can I run
(from ob in Ob_list orderby ob.f1 ascending)
when the sorting field is represented by a string (i.e. "f1")?
Unfortunately I am not able to get it with the reflection (I am not able to do something like ob.GetType().GetField("f1"), this is not mapped into sql code).
I have several fields to possibly sort the rows, which is the best&fastest approach to this?
Thank you very much!
LINQ execution is deferred until you actually enumerate over the results or access the "count", etc. Because of this, you can build up your LINQ statement in stages.
The below code is done in C#, but I'm sure the equivalent is possible in VB.NET.
First setup your basic query:
var query = (from ob in Ob_list);
At this point, nothing has actually gone to the database due to deferred execution.
Next, conditionally add your order by components:
if (sortField == "f1")
{
query = query.OrderBy(o => o.f1);
}
else if (sortField == "f2")
{
query = query.OrderBy(o => o.f2);
}
else
{
//...
}
And finally, collect your results
foreach (var item in query)
{
// Process the item
}
I've found this question: How do I specify the Linq OrderBy argument dynamically?
I'm using Entity Framework, so the first answer did not solved my problem. The second one however, worked great!
Hope it helps!
Let's say I have database with two tables - Groups and Items.
Table Groups has only two columns: Id and Name.
Table Items has three columns: Id, GroupId and Name.
As you can see, there is one-to-many relation between Groups and Items.
I'm trying to build a web service using WCF and LINQ. I've added new LINQ to SQL classes file, and I've imported these two tables. Visual Studio has automatically generated proper classes for me.
After that, I've create simple client for the service, just to check if everything is working. After I call GetAllGroups() method, I get all groups from Groups table. But their property Items is always null.
So my question is - is there a way to force WCF to return whole class (whole Group class and all Items that belong to it)? Or is this the way it should behave?
EDIT: This is function inside WCF Service that returns all Groups:
public List<Group> GetAllGroups()
{
List<Group> groups = (from r in db.Groups select r).ToList();
return groups;
}
I've checked while debugging and every Group object inside GetAllGroups() function has it's items, but after client receives them - every Items property is set to null.
Most likely, you're experiencing the default "lazy-loading" behavior of Linq-to-SQL. When you debug and look at the .Items collection - that causes the items to be loaded. This doesn't happen however when your service code runs normally.
You can however enforce "eager-loading" of those items - try something like this:
(see Using DataLoadOptions to Control Deferred Loading or LINQ to SQL, Lazy Loading and Prefetching for more details)
public List<Group> GetAllGroups()
{
// this line should really be where you *instantiate* your "db" context!
db.DeferredLoadingEnabled = false;
DataLoadOptions dlo = new DataLoadOptions();
dlo.LoadWith<Group>(g => g.Items);
db.LoadOptions = dlo;
List<Group> groups = (from r in db.Groups select r).ToList();
return groups;
}
Do you get the Items collection populated now, when you call your service?
Lets say I have a model, Foo, which is big and has lots of components. For a given Ajax query I'm only interested in one particular attribute, bar, which is a column in the foos table.
Is there a simple way I could load just that attribute, and not bother with retrieving the rest of the record? For instance if all I want to know is the bar for Foo with id#__, how could I retrieve that?
You can return only specific columns by calling the select method with a string containing the attributes you want to return. For your example:
Foo.select('bar').first #<Foo bar: 1>
Keep in mind that these objects will act like normal ActiveRecord objects but return nil for any field you did not select, so take care using this functionality.
You can call select on the class name itself or any Relation, so you can chain together the ActiveRecord calls you usually use like where, etc.
I prefer this
User.where(:id => user_id).pluck(:user_name).first #'tom'
Foo.where(:age => 23).pluck(:user_name) #['tom', 'jerry', ...]
Foo.where(<condition>).select('fieldname')
Example
results = Foo.where('is_active = ?', true).select('bar')
Access the selected fields as:
results.map {|res| res.bar} returns an array of bar's
pluck(*column_names)
doc: http://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck
e.g. Foo.pluck(:bar)
pick(*column_names) select just one top row's columns, docs
Similar to pluck but fetch only one row