In C++ code:
class CWindowUI {
public CWindowUI(const char* title,int width,int height);
.....
};
static int CreateWindow(lua_State *l)
{
int width,height;
char *title;
CWindowUI **winp, *win;
name = (char *) luaL_checkstring(l, 1);
width= lua_tounsigned(l, 2);
height= lua_tounsigned(l, 3);
win = new CWindowUI(title,width,height);
if (win == NULL) {
lua_pushboolean(l, 0);
return 1;
}
winp = (CWindowUI **) lua_newuserdata(l, sizeof(CWindowUI *));
luaL_getmetatable(l, "WindowUI");
lua_setmetatable(l, -2);
*winp = win;
return 1;
}
In Lua code:
local win = CreateWindow("title", 480, 320);
win:resize(800, 600);
Now my question is:
Function CreateWindow will return a object named win and the function resize is not defined. How do I get a notification when I call an undefined function in Lua?
The notification shall include the string "resize" and the arguments 800,600.
I want to modify the source to map the undefined function onto the callback function but it is incorrect .
How do I get a notification when I call an undefined function in lua.
You don't. Not in the way that you mean it.
You can hook an __index metamethod onto your registered "WindowUI" metatable (*groan*). Your metamethod will only get the userdata it was called on and the key that was used.
But you cannot differentiate between a function call and simply accessing a member variable, since Lua doesn't differentiate between these. If you return a function from your metamethod, and the user invokes the function-call operator on the return from the metamethod, then it will be called. Otherwise, they get a function to play with as they see fit. They can store it, pass it around, call it later, whatever. It's a value, like any other.
Related
I've implemented an IMvxNavigationFacade for deep linking in my MvvmCross 5.6.x sample app. I've added logic in BuildViewModelRequest() to construct a MvxViewModelRequest with parameters passed in as MvxBundle.
if (url.StartsWith("http://www.rseg.net/rewards/"))
{
var parametersBundle = new MvxBundle();
var id = url.Substring(url.LastIndexOf('/') + 1);
parametersBundle.Data.Add("id", id);
return Task.FromResult(
new MvxViewModelRequest(typeof(RewardDetailViewModel),
parametersBundle, null));
}
However, this approach causes the old style Init() method to be called in the target ViewModel rather than the new typesafe Prepare() method.
public class RewardDetailViewModel :
MvxViewModel<RewardDetailViewModel.Parameteres>
{
...
public new void Init(string id)
{
if (!string.IsNullOrWhiteSpace(id))
{
if (int.TryParse(id, out _rewardId))
RaiseAllPropertiesChanged();
}
}
public override void Prepare(Parameteres parameter)
{
if (parameter != null)
{
_rewardId = parameter.RewardId;
RaiseAllPropertiesChanged();
}
}
}
Is there a way to construct a MvxViewModelRequest so that you pass in an instance of the parameter class for the target ViewModel causing the Prepare() method to be called?
The entire solution can be viewed on GitHub https://github.com/rsegtx/So.MvvmNav2
Thanks in advance!
After doing some research I found at lease one way to accomplish this.
Create a ViewModelInstanceRequest rather than a ViewModelRequest so that you can call ViewModelLoader.LoadViewModel passing in a parameters object; the ViewModelRequest only allows parameters to be passed using a MvxBundle. Make the following change to BuildViewModelRequest() on the NavigationFacade:
var request = new
MvxViewModelInstanceRequest(typeof(RewardDetailViewModel));
var parameters = new RewardDetailViewModel.Parameteres();
.... parse parameters and fill in parameters object
request.ViewModelInstance = ViewModelLoader.LoadViewModel(
request, parameters, null);
return Task.FromResult((MvxViewModelRequest)request);
Create your own IMvxNavigationService and add logic to inspect the object returned from the NavigationFacde and if it is a ViewModelInstanceRequest then use it as is rather than one previously creating.
var facadeRequest = await facade.BuildViewModelRequest(path,
paramDict).ConfigureAwait(false);
...
if (facadeRequest is MvxViewModelInstanceRequest)
request = facadeRequest as MvxViewModelInstanceRequest;
else
{
facadeRequest.ViewModelType = facadeRequest.ViewModelType;
if (facadeRequest.ParameterValues != null)
{
request.ParameterValues = facadeRequest.ParameterValues;
}
request.ViewModelInstance = ViewModelLoader.LoadViewModel(
request, null);
}
I've updated the original example on GitHub https://github.com/rsegtx/So.MvvmNav2.
I have been trying to assign class's member function to a std::function but it throws compile time error Failed to specialize function template 'unknown-type std::invoke(_Callable &&,_Types &&...)
Below is the header file of that class :
class TypeAnalysis {
public:
bool AnalysisHelper(std::string filePath);
void createTypeTable(std::string dir, std::string pattern, size_t nThread = 3);
std::vector<std::string> getFiles(std::string dir, std::vector<std::string> patterns);
private:
};
And below is createtypeTable function where I am assigning AnalysisHelper method to std::fnuction object.
void TypeAnalysis::createTypeTable(std::string dir, std::string pattern, size_t nThread)
{
Threadpool<bool, std::string> tp(10);
DataContext dc;
tp.start();
std::vector<std::string> patterns = SH::split(pattern);
std::vector<std::string> files = getFiles(dir, patterns);
std::function<bool(std::string)> w = &TypeAnalysis::AnalysisHelper; //I think issue is here
try {
if (files.size() > 0) {
for (size_t i = 0; i < files.size(); i++) {
WorkItem<bool, std::string> *wi1 = new WorkItem<bool, std::string>(&w, &files[i]);
tp.doWork(wi1);
}
}
}
catch (std::exception ex) {
std::cout << ex.what();
return;
}
tp.doWork(nullptr);
tp.wait();
DataContext::getContextThreadPool().doWork(nullptr);
}
When I tried to do the same without any class definition (AnalysisHelper was Glabal function and main had same body as createTypeTable), it worked fine.
Any idea whats wrong?
Yes, the problem is in this line:
std::function<bool(std::string)> w = &TypeAnalysis::AnalysisHelper;
I can not see this as correct operation. You are referencing a member function of a class. This member function may need to edit or read one of the member variables of that class. It is not a free function. It is part of the class which should be called for a specific object. So it is normal that C++ denied that.
Edit:
I found this https://isocpp.org/wiki/faq/pointers-to-members#memfnptr-vs-fnptr
How do I pass a pointer-to-member-function to a signal handler, X event callback, system call that starts a thread/task, etc?
Don’t.
Because a member function is meaningless without an object to invoke it on,
you can’t do this directly (if The X Window System was rewritten in
C++, it would probably pass references to objects around, not just
pointers to functions; naturally the objects would embody the required
function and probably a whole lot more)
Issue was I was not binding the method to any object. Changing
std::function<bool(std::string)> w = &TypeAnalysis::AnalysisHelper;
to
std::function<bool(std::string)> w = [=](std::string file) { return this->AnalysisHelper(file); };
worked.
Is it possible to test if a value is a function that can be called? I can test for null easily but after that I have no idea how to ensure the parameter passed in is actually a function?
void myMethod(funcParam)
{
if (funcParam != null)
{
/* How to test if funcParam is actually a function that can be called? */
funcParam();
}
}
void myMethod(funcParam) {
if(funcParam is Function) {
funcParam();
}
}
Of course, the call to funcParams() only works if the parameter list matches - is Function doesn't check for that. If there are parameters involved, one can use typedefs to ensure this.
typedef void MyExpectedFunction(int someInt, String someString);
void myMethod(MyExpectedFunction funcParam, int intParam, String stringParam) {
if(funcParam is MyExpectedFunction) {
funcParam(intParam, stringParam);
}
}
In your case, you want to check if the function can be called with zero arguments.
typedef NullaryFunction();
main () {
var f = null;
print(f is NullaryFunction); // false
f = () {};
print(f is NullaryFunction); // true
f = (x) {};
print(f is NullaryFunction); // false
}
If you just want to know that it is some function, you can test with ... is Function. All callable objects implement Function, but it is technically possible (though often not useful) to implement Function manually without actually being callable. It does make a kind of sense for objects that mock callability through noSuchMethod.
var f = () {};
print(f is Function); // 'true'
var x = (x){};
print(x is Function); // 'true'
love how Dart treats function arguments, but cannot accomplish what should be a simple task:
void func( String arg1, [ Map args = {} ] ) {
...
}
get the error
expression is not a valid compile-time constant
have tried new Map() for example, with same error.
You have to use the const keyword :
void func( String arg1, [ Map args = const {} ] ) {
...
}
Warning : if you try to modify the default args you will get :
Unsupported operation: Cannot set value in unmodifiable Map
The default value must be a compile time constant, so 'const {}' will keep the compiler happy, but possibly not your function.
If you want a new modifiable map for each call, you can't use a default value on the function parameter. That same value is used for every call to the function, so you can't get a new value for each call that way.
To create a new object each time the function is called, you have to do it in the function itself. The typical way is:
void func(String arg1, [Map args]) {
if (args == null) args = {};
...
}
I am trying to understand the way the AsyncToken works in actionscript. How can I call a remote service and ensure that a specific parameter is available in the result or fault event functions? I think it is the async functionality I want to use.
The following code will hopefully explain what I am trying to do. Feel free to modify the code block as your explanation.
Thanks.
public function testSerivceCall(data:Object, callBackCommand:String):void
{
// Assume callBackCommand == "FOO";
// How can I pass in callBackCommand as a parameter to the result or fault events?
// How do I create an async token here?
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
remoteObject.test(data);
}
private function _handleTestResult( event:ResultEvent ) : void
{
// How do I get the async token value?
// How can I get the value of callBackCommand in this code block?
if (callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
// How do I get the async token value?
// How can I get the value of callBackCommand in this code block?
}
An edit to make this question more clear:
Assume I make the following method call somewhere in my code:
testSerivceCall(personObject, "LoginCommand");
How do I get access to the actual string "LoginCommand" inside the _handleTestResult function block?
The reason I want to do this is because I want to dynamically call back certain functions and hand off the result data to specific commands that I know ahead of time when I am making the service call.
I am just having a time grokking the AsyncToken syntax and functionality.
I did not even need closures. I added a class as below which I called externally.
The call was like this:
public class MyClass
{
...
var adminServerRO:AdminServerRO = new AdminServerRO();
adminServerRO.testSerivceCall("FOO",cptyId);
}
public class AdminServerRO
{
private function extResult( event:ResultEvent, token:Object ) : void
{
//the token is now accessed from the paremeter
var tmp:String = "in here";
}
private function extFault( event:FaultEvent ) : void
{
var tmp:String = "in here";
}
public function testSerivceCall(callBackCommand:String, cptyId:String):void
{
var remoteObject:RemoteObject = new RemoteObject();
remoteObject.destination = "adminServer";
var token:AsyncToken = remoteObject.getCounterpartyLimitMonitorItemNode(cptyId);
token.addResponder(new AsyncResponder(extResult,extFault,cptyId));
}
}
While the accepted answer will accomplish what the original submitter wants it does not actually answer the question which was asked. An AsyncToken is created as a result of a remote method call and is accessible from the ResultEvent. Since AsyncToken is a dynamic class you can add whatever property to it that you want. The code below should demonstrate this:
public function testSerivceCall(data:Object, callBackCommand:String):void
{
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
var token:AsyncToken = remoteObject.test(data);
token.callBackCommand = callBackCommand;
}
private function _handleTestResult( event:ResultEvent ) : void
{
if (event.token.callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
//event.token.callBackCommand should be populated here too
}
If you want to access the properties used during the remote call (parameters to the call and/or AsycToken), you can make use of closures. Just define the result event handler inside the calling method as a closure. It can then access any variable in the calling function.
public function testSerivceCall(data:Object, callBackCommand:String):void
{
var _handleTestResult:Function = function( event:ResultEvent ) : void
{
// token is visible here now
if (callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
var token = remoteObject.test(data);
}
If I'm reading your question correctly, you're trying to figure out how to access the actual data returned by the ResultEvent ?
If so, assuming you've made the call correctly and you've gotten data back in a format you're expecting:
private function _handleTestResult( event:ResultEvent ) : void
{
// you get the result from the result property on the event object
// edit: assuming the class Person exists with a property called name
// which has the value "John"
var person : Person = event.result as Person;
if (person.name == "John")
{
Alert.show("John: " + person.name);
}
else
{
Alert.show("Not John: " + person.name);
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
// Maybe you know the type of the returned fault
var expectedFault : Object = event.fault as MyPredefinedType
if (expectedFault.myPredefinedTypesPredefinedMethod() == "BAR")
{
// something here
}
}
The ResultEvent has a property called result which will hold an instance of the object returned by the result (it might be the output of an XML file if using a web service, or a serialized object if using AMF, for example). This is what you want to access. Similarly, FaultEvent has a fault property that returns the fault information.
Edit: Changed code in _handleTestResult() in response to Gordon Potter's comment.