I am working on a web api project (back end) and I am searching for some more optimized way to get multiple parameter from front end. There are numerous ways like
i) name each parameter in action parameter stack
ii) extract from request body like Request.Content.ReadAsStringAsync().Result;
iii) define complex types (model) and use that type to receive values. like MyAction(UserLog log)
I have to create hundreds of functions which may take variable number of parameters. I don't want to use first option above, it is hectic for large data.
The second is confusing as no one can predict what to post.
The third one forces me to create hundreds of input models. So is there any better way to do so?
You could try using a form data collection
Its basically a Key Value Pair which allows for an element of genericness.
Edit - another link
Another option would be to apply dynamic object parameters on your Post Verbs.
E.g.
public string Post(dynamic value)
{
string s = "";
foreach (dynamic item in value)
{
s = s + item.content + " ";
}
return s;
}
Related
I have written an AggregateFactory Vertica UDF which returns a single value
getReturnTypes(si,columnTypes args,columnTypes returnTypes){
returnTypes.addVarbinary(512);
//I want to add second returnType
returnTypes.addFloat("");
}
getProtoType(si,columnTypes args,columnTypes returnTypes){
returnTypes.addVarbinary(512);
//I want to add second returnType
returnTypes.addFloat("");
}
this is not working, how can I return two values from an AggregateFactory UDF?
You cannot. User Defined Aggregate Functions (as explained in the fine manual) return ONE value per group. You might want to write a User Defined Transform Function (maybe a multi-phase Transform Function).
I am using GrapgQL and Java. I need to extract all the children belongs to specific parent. I have used the below way but it will fetch only the parent and it does not fetch any children.
schema {
query: Query
}
type LearningResource{
id: ID
name: String
type: String
children: [LearningResource]
}
type Query {
fetchLearningResource: LearningResource
}
#Component
public class LearningResourceDataFetcher implements DataFetcher{
#Override
public LearningResource get(DataFetchingEnvironment dataFetchingEnvironment) {
LearningResource lr3 = new LearningResource();
lr3.setId("id-03");
lr3.setName("Resource-3");
lr3.setType("Book");
LearningResource lr2 = new LearningResource();
lr2.setId("id-02");
lr2.setName("Resource-2");
lr2.setType("Paper");
LearningResource lr1 = new LearningResource();
lr1.setId("id-01");
lr1.setName("Resource-1");
lr1.setType("Paper");
List<LearningResource> learningResources = new ArrayList<>();
learningResources.add(lr2);
learningResources.add(lr3);
learningResource1.setChildren(learningResources);
return lr1;
}
}
return RuntimeWiring.newRuntimeWiring().type("Query", typeWiring -> typeWiring.dataFetcher("fetchLearningResource", learningResourceDataFetcher)).build();
My Controller endpoint
#RequestMapping(value = "/queryType", method = RequestMethod.POST)
public ResponseEntity query(#RequestBody String query) {
System.out.println(query);
ExecutionResult result = graphQL.execute(query);
System.out.println(result.getErrors());
System.out.println(result.getData().toString());
return ResponseEntity.ok(result.getData());
}
My request would be like below
{
fetchLearningResource
{
name
}
}
Can anybody please help me to sort this ?
Because I get asked this question a lot in real life, I'll answer it in detail here so people have easier time googling (and I have something to point at).
As noted in the comments, the selection for each level has to be explicit and there is no notion of an infinitely recursive query like get everything under a node to the bottom (or get all children of this parent recursively to the bottom).
The reason is mostly that allowing such queries could easily put you in a dangerous situation: a user would be able to request the entire object graph from the server in one easy go! For any non-trivial data size, this would kill the server and saturate the network in no time. Additionally, what would happen once a recursive relationship is encountered?
Still, there is a semi-controlled escape-hatch you could use here. If the scope in which you need everything is limited (and it really should be), you could map the output type of a specific query as a (complex) scalar.
In your case, this would mean mapping LearningResource as a scalar. Then, fetchLearningResource would effectively be returning a JSON blob, where the blob would happen to be all the children and their children recursively. Query resolution doesn't descent deeper once a scalar field is reached, as scalars are leaf nodes, so it can't keep resolving the children level-by-level. This means you'd have to recursively fetch everything in one go, by yourself, as GraphQL engine can't help you here. It also means sub-selections become impossible (as scalars can't have sub-selections - again, they're leaf nodes), so the client would always get all the children and all the fields from each child back. If you still need the ability to limit the selection in certain cases, you can expose 2 different queries e.g. fetchLearningResource and fetchAllLearningResources, where the former would be mapped as it is now, and the latter would return the scalar as explained.
An object scalar implementation is provided by the graphql-java ExtendedScalars project.
The schema could then look like:
schema {
query: Query
}
scalar Object
type Query {
fetchLearningResource: Object
}
And you'd use the method above to produce the scalar implementation:
RuntimeWiring.newRuntimeWiring()
.scalar(ExtendedScalars.Object) //register the scalar impl
.type("Query", typeWiring -> typeWiring.dataFetcher("fetchLearningResource", learningResourceDataFetcher)).build();
Depending on how you process the results of this query, the DataFetcher for fetchLearningResource may need to turn the resulting object into a map-of-maps (JSON-like object) before returning to the client. If you simply JSON-serialize the result anyway, you can likely skip this. Note that you're side-stepping all safety mechanisms here and must take care not to produce enormous results. By extension, if you need this in many places, you're very likely using a completely wrong technology for your problem.
I have not tested this with your code myself, so I might have skipped something important, but this should be enough to get you (or anyone googling) onto the right track (if you're sure this is the right track).
UPDATE: I've seen someone implement a custom Instrumentation that rewrites the query immediately after it's parsed, and adds all fields to the selection set if no field had already been selected, recursively. This effectively allows them to select everything implicitly.
In graphql-java v11 and prior, you could mutate the parsed query (represented by the Document class), but as of v12, it will no longer be possible, but instrumentations in turn gain the ability to replace the Document explicitly via the new instrumentDocument method.
Of course, this only makes sense if your schema is such that it can not be exploited or you fully control the client so there's no danger. You could also only do it selectively for some types, but it would be extremely confusing to use.
I have a treeview and want to get notified if the selection changes. What is the signature for the callback?
I found a code snippet like:
Gtk::TreeView *treeview = Gtk::manage(new Gtk::TreeView);
Glib::RefPtr< Gtk::TreeSelection > sel = treeview->get_selection();
sel->set_mode( Gtk::SELECTION_MULTIPLE );
sel->set_select_function(sigc::ptr_fun(&SelFun));
But I can't find anything about the SelFun!
How is the signature
How to find out which rows and columns are selected inside this function?
How to access data from the model with that object
Yes, I have actually no idea how the TreeView/Model/Path/Selection interacts. Every link to an example is highly welcome!
You seem to want multiple selection. I had the same problem too. Once you have enabled mutliple selection, getting the selected rows is a little more difficult. The method of acquiring them varies slightly.
I'll provide the most general method. First, you need to overload the signal_changed() signal after you have enabled multiple selection. Then, assign the TreeView's TreeSelection to a RefPtr for easy access.
Glib::RefPtr<Gtk::TreeSelection> TreeView_TreeSelection;
TreeView_TreeSelection = your_TreeView.get_selection();
Next, connect the TreeSelection to the signal_changed() signal.
TreeView_TreeSelection -> signal_changed().connect(sigc::mem_fun(your_TreeView,
&your_Class::on_selection_changed));
Now, make sure to make a void function header in "your_Class" named on_selction_changed() or whatever you want. Just make sure to change the name in the connection above to whatever your class' name is.
The final step is to make the function. Here is a simple example of getting a vector of all of the TreePaths of the rows selected, then converting those TreePaths into a vector of TreeModel::Row pointers.
void your_Class::on_selection_changed()
{
if((TreeView_TreeSelection -> count_selected_rows()) == 0)
{
return;
}
vector<Gtk::TreeModel::Path> selected_rows = TreeView_TreeSelection -> get_selected_rows();
vector<Gtk::TreeModel::Row*> selected_TreeRows;
vector<Gtk::TreeModel::Path>::iterator TreePath_iterator = selected_rows.begin();
Gtk::TreeRow *row;
while(TreePath_iterator != selected_rows.end()
{
selected_row_it = p_TreeModel -> get_iter(TreePath_iterator);
row = (*selected_row_it);
selected_TreeRows.push_back(row);
TreePath_iterator++;
}
}
Do you know how to iterate through a TreeModel using the STL-like contain API called children() of a TreeModel? It's most useful for iterating over all of the rows of a TreeModel or getting the size (AKA row count) of a TreeModel. Its use depends on whether you're using a ListStore, TreeStore or a custom TreeModel.
I have a method drive that goes like this:
public double drive(double milesTraveled, double gasUsed)
{
gasInTank -= gasUsed;
return totalMiles += milesTraveled;
}
I know I can't return multiple values from a method, but that's kind of what I need to do because I need both of these values in my main method, and as it is now it's obviously only returning the one. I can't think of anything that would work. Sorry if this is a super beginner question. What can I do to get both values to return from the method?
You can return multiple value from a function. To do this You can use structure.
In the structure you can keep required field and can return structure variable after operation.
You can also make a class for the required field if You are using OOPS supporting language but Structure is best way.
In most languages you can only return a single value from a method. That single value could be a complex type, such as a struct, array or object.
Some languages also allow you to define output parameters or pass in pointers or references to outside storage locations. These kinds of parameters also allow you to return additional values from your method.
not sure, but can you take array of your values?
array[0]=gasInTank;
array[0] -= gasUsed;
array[1]=milesTraveled;
array[1] -= milesTraveled;
return array;
I am wondering if anyone can suggest me a design pattern or best way to code the below problem.
1) I have an array list of books like the below
list.add(new Book(title, author);
list.add(new Book(title1, author1);
and so on....
2) And now I would like to find all the books from the list by author
findByAuthor(String author) {
for(Book book : list){
if(book.getAuthor().equals(author)){
return book;
}
}
}
Like wise I have another method called findByTitle(). But, it would be same code except book.getAuthor() will have to be book.getTitle(). Everything will be same.
3) Now i can write a method which is generic to both methods like below;
findByBookProperty (String type, String propertyValue){
for(Book book : list)
if(type.equals("author") && book.getTitle().equals(propertyValue)){
return book;
} //another else if for author
//another else for another property
// if else repeats for all the required finder types...
}
}
4) The problem i have here is;
1. I dont want to use the nasty if/else condition for the finder types.
2. I want to know if there is any design pattern or better way to handle this if else or swich method.
Important note: I get the author name as a request parameter value in my spring controller method.
I appreciate your thoughts.
Use Commons-Collections' Predicates framework:
1) Construct a Predicate instance for each type of test.
2) Use CollectionUtils.select(), passing in the predicate you'd like to use for evaluating objects.
Another alternative is to use Commons-Collections' Transformation framework:
1) Write a Transformer for each type of property you'd like extracted/compared against.
2) Write a generic loop, accepting a Transformer instance as a parameter.