reference

问题 I use the method described in Firestore how to get the collection value from another collection document id is referenced but i've to combinate two reference document in one time but in other collections like: cash.models.ts: import { DocumentReference } from "@angular/fire/firestore"; export class Cash { // .collection('contactors') id: string; person: DocumentReference<Workers>; contactor: DocumentReference<Contactors>; nr_dokumentu: string; kwota: number; data: string; } export class

问题 I have since changed my implementation to not do this anymore, but I would be interested in knowing if the following could lead to issues - take for example a process that has multiple steps, each involving passing a reference to an NSError object. If you were to reuse this error object each step along the way, would that reference be negatively effected in some way, perhaps leading to some sort of memory management/dealloc crash? Example (most of the in-between code has been omitted) NSError

问题 I am currently trying to use pHash.dll on http://phash.org Unfortunately it was written in C++, I'd have to use DLLImport But the problem I am having is how to register pHash.dll (compiled thru VS2010/C++) I've tried to register using regsrv32 and have been fruitless giving an error message. Now, How can i register pHash to show up in COM tab? 回答1: The DLL in question exports flat APIs. The Add COM References Tab is for DLLs that expose COM objects. Instead of using Add Reference to refer to

问题 I have a tiny playground example here fn main() { let l = Some(3); match &l { None => {} Some(_x) => {} // x is of type &i32 } } I'm pattern matching on &Option and if I use Some(x) as a branch, why is x of type &i32 ? 回答1: The type of the expression &l you match against is &Option<i32> , so if we are strict the patterns should be &None and &Some(x) , and if we use these patterns, the type of x indeed is i32 . If we omit the ampersand in the patterns, as you did in your code, it first looks

问题 This question already has answers here : Why is it illegal/immoral to reseat a reference? [duplicate] (5 answers) Why are references not reseatable in C++ (17 answers) Closed 6 years ago . I read about C++ reference variables and somewhere I found this: A declaration of a const reference is redundant since reference can never be made to refer to another object. what does it mean? Here, for example, I can change the object that the reference is referring to: void p(int& i) { int a = 7,c = 0; i

问题 Using VB.NET, trying to write a page title to a text file. I am stumped here: Private Sub Dim pagetitle As String pagetitle = WebBrowser1.Document.Title My.Computer.FileSystem.WriteAllText("page title.txt", pagetitle, False) But I get an error saying "Object reference not set to an instance of an object." Please help! 回答1: Most likely you are trying to access the Document property when it is still equal to Nothing . Move your code to the DocumentCompleted event of the WebBrowser control, as

问题 I'm using joomla and i have read through the API and I noticed the JFactory class having functions return a reference to the object but the examples I have gathered from the internet do not use the & when using the functions. Say for example the Jfactory::getSession() which returns a reference to the global session. the documentation shows that its defined as function &getSession(params){code} - clearly defining a reference return. however, in this example, they call it as $session = JFactory

问题 While searching for some loosely related stuff I bumped into this quote: And a reference can outlive an object and be used to refer to a new object created at the same address. From this answer. Now, I've always known and worked by references being immutable, initialized once and all that. Reading the above quote, by someone likely more experienced than I am, got me wondering if I'm missing something. Was that sentence meant to be for the sake of completeness but practically inapplicable? Is

问题 I saw How can I redefine Perl class methods?, so I wanted to understand better how it works through an example. (Related: How do I reference methods? - PerlMonks) If I have an object $obj which is an instance of some Class which has Class::method , then $obj also has $obj->method ; I assume the simplified memory layout in that case would look something like this (tables made in LaTeX Table Generator; for the below one, src here): ... that is, at (say) address 0x1000 we have the $obj->method ,

问题 In the following function, I want to take a vector objects and return a copy of one of the elements of that vector. Since the code below compiles correctly, I'm assuming that the iterator copy_objects.back() is automatically dereferenced. But I don't know for certain. What is happening in the return statement? MyObject best(vector<MyObject>& objects) { vector<MyObject> copy_objects = objects; sort(copy_objects.begin(), copy_objects.end(), compare_MyObject_func); return copy_objects.back(); }