descriptor

问题 So after my circular dependency problem with the BGL was solved I've come to another obstacle. I'm currently using an adjacency-list to model my graph. Bundled properties for both nodes and edges are applied to store some information in the graph. So I have something like this: class Node { int x, int y // position }; class Edge { float length; }; boost::adjacency_list<boost::listS, boost::listS, boost::directedS, Node, Edge> The problem arises when I want to store shortcuts to specific nodes

问题 I´m developing an BLE app, based on the Gatt sample project provided by google: https://developer.android.com/samples/BluetoothLeGatt/index.html. So, I can send data writing in a characteristic successfully. Now I need to know when this characteristic change its value. DeviceActivity private void displayGattServices(List<BluetoothGattService> gattServices) { // get services & characteristics ................ final BluetoothGattCharacteristic characteristic = mGattCharacteristics.get(2).get(0)

问题 I was reading the tutorial on this page: http://edocs.bea.com/docs/cd/E13222_01/wls/docs81/medrec_tutorials/ejbgen.html#858279 And I have the following file BankAccountEJB.java import javax.ejb.CreateException; import javax.ejb.EntityBean; import javax.ejb.EntityContext; public abstract class BankAccountEJB implements EntityBean { private EntityContext context; public void setEntityContext(EntityContext aContext) { context = aContext; } public void ejbActivate() { } public void ejbPassivate()

问题 The Documentation of OpenCV mentions the function "train()" within a DescriptorMatcher. "virtual void cv::cuda::DescriptorMatcher::train ( ) pure virtual Trains a descriptor matcher. Trains a descriptor matcher (for example, the flann index). In all methods to match, the method train() is run every time before matching."(docs) That's all is said there. Does someone know hot it works? Especially what the DescriptorMatcher needs to train itself. A short example in some OOP language would be

问题 Does anyone have any tips or good practices for testing Python descriptors? I'm writing some descriptors to encapsulate data validation and want to write tests for them. For one thing, I'm wondering if I should test them by creating instances of the descriptors in my tests and then calling the __get__ or __set__ methods explicitly. Or should I create a special class in my test file which uses the descriptor class and then use that class in my tests? Or should I add the descriptor to my

问题 I am trying to make custom type system in Python. Following is the code. from inspect import Signature, Parameter class Descriptor(): def __init__(self, name=None): self.name = name def __set__(self, instance, value): instance.__dict__[self.name] = value def __get__(self, instance, cls): return instance.__dict__[self.name] class Typed(Descriptor): ty = object def __set__(self, instance, value): if not isinstance(value, self.ty): raise TypeError('Expected %s' %self.ty) super().__set__(instance

问题 In a Spring 3 app a controller is calling a JpaCollectorManager with calls a JpaCollectorInfoDao to get a list which is defined by a nativequery. The query calls 2 seperate tables which uses sql and jpql because I need to use a postgresql feature not implemented in jpql. When the controller tries to file the list I get the following error message: Exception [EclipseLink-6007] (Eclipse Persistence Services - 2.1.2.v20101206-r8635): org.eclipse.persistence.exceptions.QueryException Exception

问题 I am learning Python, and I am trying to understand descriptors better. When I look at this Python online book: http://www.cafepy.com/article/python_attributes_and_methods/ch01s05.html, it says: If attrname is a special (i.e. Python-provided) attribute for objectname, return it. I don't understand what Python-provided means. Can someone give me an exemple of such Python-provided attribute that would take precedence over the usual resolution order? Note: I am only interested in new-style

问题 This question already has answers here : Can a method be used as either a staticmethod or instance method? (4 answers) Closed 6 years ago . Can I define a Python method to be both static and instance at the same time? Something like: class C(object): @staticmethod def a(self, arg1): if self: blah blah So that I can call it with both: C.a(arg1) C().a(arg1) The intent is to be able to run two sets of logics. If accessed as an instance method, it would make use of instance variables and do stuff

问题 In class B below I wanted the __set__ function in class A to be called whenever you assign a value to B().a . Instead, setting a value to B().a overwrites B().a with the value. Class C assigning to C().a works correctly, but I wanted to have a separate instance of A for each user class, i.e. I don't want changing 'a' in one instance of C() to change 'a' in all other instances. I wrote a couple of tests to help illustrate the problem. Can you help me define a class that will pass both test1