quick question regarding querying a graph database in Titan using a Cassandra back end.
Splitting the problem down into it's simplest form, say I have a relationship that goes something like this:
node1 ----------> node2
When loading in data, I have assigned a number of properties to each edge using the e.setProperty("name",value) command. Say I have three properties called property1, property2 and property3. What I'd like to do is return the value of a certain property, say property1. My code looks like this:
g.E(1).getProperty("property1")
However it returns null. Does anyone know the correct way of adding edge properties and querying them appropriately?
getProperty() is only for a single object (vertex or edge). What you have, is a pipe. You can use either:
g.E().property("property1")
or:
g.E().property1
or:
g.E().next().getProperty("property1")
Related
I need some guidance on how to add a drop down list from an array of data after the read info from the MP4 Tag data is parsed. The mechanism I'm using is 100% operational, this is a creature feature addition. The MP4 tag I'm working with is Genre using the ID3V1 standard. There are 191 choices. The way my app was inherited, there are 2 columns, property/value and multiple rows. All of that works. The Genre tag was setup willy nilly so you could basically type whatever and it would store it. I want to remove that and have the 191 elements in the array to choose from using the drop down list. Part of the loading process is that it will pull in whatever was in the MP4 file. So, I want the user to be able to leave as is (most likely tagged by something that supports ID3V2), or select from the populated 191 elements in the dropdown list.
The object looks like this information.h:
protected:
CMFCPropertyGridCtrl m_wndProperties;
The information.cpp looks like this:
void CInformationView::OnInitialUpdate()
{
// create property grid
VERIFY(m_wndProperties.Create(WS_CHILD|WS_VISIBLE|WS_TABSTOP| WS_BORDER, CRect(0,0,0,0), this, 0));
// get document
CMovieDoc *lpkDoc = GetDocument();
ASSERT_VALID_PTR(lpkDoc);
// add properties //Information ORDER Loading <<<<< List shortened Stack overflow question
m_wndProperties.AddProperty(lpkDoc->m_pkArtist);
m_wndProperties.AddProperty(lpkDoc->m_pkTempo);
m_wndProperties.AddProperty(lpkDoc->m_pkGenre);
CView::OnInitialUpdate();
}
The way it pulls the data in from mp4.cpp:
// Genre
m_pkGenre = new CMFCPropertyGridProperty(_T("Genre"),
COleVariant(AfxStringFromUtf8(lptTags->genre), VT_BSTR));
The pointers in mp4.h:
CMFCPropertyGridProperty *m_pkArtist;
CMFCPropertyGridProperty *m_pkTempo;
CMFCPropertyGridProperty *m_pkGenre;
Now I know that pull downs in the 2nd column (Values) can be done because other tags have simple TRUE/FALSE that can be selected, so that tells me it should be possible to create the drop down list I'm looking to do. An example of the TRUE/FALSE looks like this:
// Compilation
m_pkCompilation = new CMFCPropertyGridProperty(_T("Compilation"),
COleVariant((!VALID_PTR(lptTags->compilation)) ? (short)0 : (short)*lptTags->compilation, VT_BOOL));
I've done arrays in C for things like microcontrollers, but not entirely sure if it is the same in C++. I'm thinking it should look like this:
// Initialize Genre Array
const char *genre[4] = { "Rock", "Rap", "Soul", "House" };
The questions are:
How do I create an the array (or does my example above look correct?) to house fixed strings like "Rock", "Rap", "Soul", etc. etc?
How to modify the VALUE row to have the pull down that contains the parsed Genre tag present and then when opened, show the 191 Genre tags where one can be selected to choose from (and ultimately save which is already working).
Actual code, not references to the learn.microsoft.com, the few things I've tried crashes when I try to alter the AddProperties I assume because of the lpkDoc pointers being used.
You should not use a plain old C-style array if you do not have a strong reason to. Use a std::vector instead. You don't even need to indicate the [size].
The same goes for char *. Use a CString or astd::string instead.
const std::vector<CString> = { L"Rock", L"Rap", L"Soul", L"House" };
Don't make your life harder than it needs to be.
2.
for (size_t i= 0; i < genre.size(); i++)
{
auto gnr= genre[i];
lpkDoc->m_pkGenre->AddOption(gnr);
}
or even better
for (auto it : genre)
{
lpkDoc->m_pkGenre->AddOption(it);
}
Important note: You should not have code about properties in your doc object. You are mixing business logic with user interaction logic. Your code in the future will be a nightmare to maintain.
I do not see your lpkDoc->m_pk variable init'ed anywhere, and I bet those pointers are pointing to no man's land.
I've finally started to understand a lot of info regarding FireStore, but I'm wondering if I can get some assistance.
If I had a setup similar to or like this:
races
Android
name: Android
size: medium
stats <---- this is the map
str: 10
sex: 12.... (more values)
How would I parse this? I am looking to make specific TextViews apply values found in the database so that I can simply update the database and my app will populate those values so that hard coding and code updating won't be nearly as troublesome in the future.
I currently use something like this:
val androidRef = db.collection("races").document("Android")
androidRef.get().addOnSuccessListener { document ->
if (document != null) {
oneOfTheTextViews.text = document.getString("str")
} else {
}
The issue is currently I can only seem to access from collection (races) / document (android) / then a single field (I have "str" set as a single field, not part of a map or array)
What would the best practice be to do this? Should I not nest them at all? And if I can reference said nesting/mapping/array, what functions need to be called? (To be clear, I am not asking only whether or not it is possible - the reference guides and documents allude to such - but what property/class/method/etc needs to be called in order to access only one of those values or point to one of those values?).
Second question: Is there a way to get a list of document names? If I have several races, and simply want to make a spinner or recycler view based on document names as part of a collection, can I read that to the app?
What would the best practice be to do this?
If you want to get the value of your str property which is nested within your stats map, please change the following line of code:
oneOfTheTextViews.text = document.getString("str")
to
oneOfTheTextViews.text = document.getString("stats.str")
If your str property is a number and not a String, then instead of the above line of code please use this one:
oneOfTheTextViews.text = document.getLong("stats.str")
Should I not nest them at all?
No, you can nest as many properties as you want within a Map.
Is there a way to get a list of document names?
Yes, simply iterate the collection and get the document ids using getId() function.
I am struggling trying to traverse an MDLAsset instance created by loading an SCNScene file (.scn).
I want to identify and extract the MDLMeshs as well as camera(s) and lights. I see no direct way to do that.
For example I see this instance method on MDLAsset:
func childObjects(of objectClass: Swift.AnyClass) -> [MDLObject]
Is this what I use?
I have carefully labeled things in the SceneKit modeler. Can I not refer to those which would be ideal. Surely, there is a dictionary of ids/labels that I can get access to. What am I missing here?
UPDATE 0
I had to resort to pouring over the scene graph in the Xcode debugger due to the complete lack of Apple documentation. Sigh ...
A few things. I see the MDLMesh and MDLSubmesh that is what I am after. What is the traversal approach to get it? Similarly for lights, and camera.
I also need to know the layout of the vertex descriptors so I can sync with my shaders. Can I force a specifc vertex layout on the parsed SCNScene?
MDLObject has a name (because of its conformance to the MDLNamed protocol), and also a path, which is the slash-separated concatenation of the names of its ancestors, but unfortunately, these don't contain the names of their SceneKit counterparts.
If you know you need to iterate through the entire hierarchy of an asset, you may be better off explicitly recursing through it yourself (by first iterating over the top-level objects of the asset, then recursively enumerating their children), since using childObjects(of:) repeatedly will wind up internally iterating over the entire hierarchy to collect all the objects of the specified type.
Beware that even though MDLAsset and MDLObjectContainerComponent conform to NSFastEnumeration, enumerating over them in Swift can be a little painful, and you might want to manually extend them to conform to Sequence to make your work a little easier.
To get all cameras,
[asset childObjectsOfClass:[MDLCamera class]]
Similarly, to get all MDLObjects,
[asset childObjectsOfClass:[MDLObjects class]]
Etc.
MDLSubmeshes aren't MDLObjects, so you traverse those on the MDLMesh.
There presently isn't a way to impose a vertex descriptor on MDL objects created from SCN objects, but that would be useful.
One thing you can do is to impose a new vertex descriptor on an existing MDL object by setting a mesh's vertexDescriptor property. See the MDLMesh.h header for some discussion.
I'm have a List<Ref<Entity>>. I add new entries to the list like this:
entities.add(Ref.create(new_entry));
modified.add(new_entry);
When I store the entity that contains the list, I store the list itself and all the entities that are in the modified list. This works fine.
The problem is, that I have to work with the entities-list, while I add new entries to it. This requires iterating the list multiple times. The problem here is, that the refs in the list point to old entries (which are already in the datastore) and new entries (which are not yet in the datastore).
This causes the Ref.get()-method to return null for all the yet unstored entries in the list (the ones that are still in the modified-list).
I worked around this by doing this when inserting:
Ref<T> ref = new DeadRef<>(
Key.create(data),
data
);
this.entities.add(ref);
this.modified.add(data);
This way, I can mix stored and unstored entries in one list and Ref.get() always returns a value.
This works, but I have noticed that the refs in the entities-list stay DeadRefs when I store them to the datastore and load them in again.
Will this be a problem? Is there maybe even a better way to accomplish this?
This seems like a bad idea, although I don't know what specific problems you will run into.
The "right answer" is to save your entities first.
Edit: Also look at the documentation for ofy().defer().save(), which can prevent you from issuing a lot of unnecessary save operations.
In my graph database I have Branches and Leaves. Branches can "contain" Leaves and Branches can "contain" Branches.
How, using Gremlin, can I find all leaves for a given branch, that are directly or indirectly related to it?
I got this to work in Cypher:
START v=node(1) MATCH v-[:contains*1..2]->i RETURN v,i
Where the *1..2 means "friends and friends of friends".
I thought maybe LoopV was the way forward, but I just get an Exception:
Error reading JArray from JsonReader. Current JsonReader item is not an array: String
You can do the following in Gremlin 1.4+.
g.v(1).out('contains').loop(1){true}{it.out('contains').count() == 0}
This says:
Start at vertex with id 1
Take the outgoing "contains" edges.
Loop over the out('contains') section.
Loop "infinitely" (make sure your tree doesn't have loops in it)
Emit only those vertices touched that don't have more outgoing 'contains'-edges. (i.e. the leaves)
However, looking at what you wanted from Cypher, it looks like you only want 2 steps. Thus, to do that, simply do:
g.v(1).out('contains').loop(1){it.loops < 3}
Perhaps I misunderstood your question --- either way, that should give you enough to play with.