reference

问题 i am trying this code, but i get this error: Only variables can be passed by reference in xxx script class page { function insert($db, $of, $form, &$arr) { $i = 0; foreach(array_combine($form['value0'], $arr) as $val=>$v){ $sql->prepare("mysqli query here"); $sql->bind_param('ssss', $val, $of, $v[$i][0], $v[$i][1]);//error here $sql->execute(); $i++; } return true; } } what is the reason, and how can be solved ? thanks 回答1: I assume you're using mysqli::bind_param. All arguments except the

问题 A base class reference variable may be assigned the address of either a base class object or a derived class object. True/False? Can anybody show me an example of what this means? I'm new to Java and am trying to understand language specific terms of Java. Thanks. I think an example of this would be the code I've written below: public class B extends A { A a = new A(); A ab = new B(); } class A { } I think that since both reference variables are valid syntax (in Eclipse) then the answer is

问题 How we can create a table of contents page dynamically in XSL-FO? 回答1: What I've done in the past is use <fo:page-number-citation> for each entry in the TOC (Table of Contents). I do the table of contents as an <fo:table> . The <fo:page-number-citation> has a ref-id attribute that should contain the id of the location you're referencing. It should generate the PDF page number where that id is located. For example, if you wanted each <chapter> referenced in your TOC, you would use <fo:page

问题 Why does the first function not modify the original array like the second function does? var a= [3, 4, 5]; function doesNothing(a) { a=[1,1,1]; } function doesSomething(a) { a.push(6); } doesNothing(a); console.log(a); // [3,4,5] not [1,1,1] doesSomething(a); console.log(a); //[3,4,5,6] 回答1: The first function makes no attempt to modify the array. All it does is assign a new value to the parameter that, when it was called, was given a copy of a reference to the array. The variable a in the

问题 Short question, is the following ok: struct X { A& x; A y; X() : x(y) {} }; Reversing the order of the two members in the struct is definitely ok, since it guarantees y is initialized first, but does this work or invoke UB? Moreso, would the following be ok: struct X { X& x; X() : x(*this) {} }; ? 回答1: I don't think that would invoke undefined behavior. I don't see that case is any different from this: int *p = new int; The expression new int is a pointer to an uninitialized int. Here we are

问题 Is there an equivalent in JavaScript for PHP's reference passing of variables? [PHP]: function addToEnd(&$theRefVar,$str) { $theRefVar.=$str; } $myVar="Hello"; addToEnd($myVar," World!"); print $myVar;//Outputs: Hello World! How would the same code look in JavaScript if possible? Thank you! 回答1: Objects are passed as references. function addToEnd(obj,$str) { obj.setting += $str; } var foo = {setting:"Hello"}; addToEnd(foo , " World!"); console.log(foo.setting); // Outputs: Hello World! Edit:

问题 In the snippet below I use $(this) to refer to the element in which the function is being called from. I know it is not correct because I printed out the values and it gave me 'undefined'. How do I refer to the input element? $(function() { $( ".datepicker" ).datepicker({ onSelect: function (date, obj){ if(confirm('Is this correct?: '+ date )) { $.post('edit.php', { "row": $(this).data('id'), "date":date, "field":$(this).name, "ajax":'true' }); } } }); }); Here is the html element: <input

问题 Excuse me, this question maybe exist in a different form but I really searched everywhere and don't see it. I have worked in C++ and am used to pointers. I am having problem with substituting my logic with C# analogue code. Here is my C# code: class Parent { public Parent A { get; set; } public Parent B { get; set; } } static void Main(string[] args) { Parent P1 = new Parent(); Parent X = new Parent(); Parent[] array = new Parent[10]; array[0] = P1; array[1] = P1.A; array[2] = P1.B; array[1]=

问题 This question already has answers here : How to copy a python class? (8 answers) Closed 5 years ago . I have been playing with the deepcopy function and the copy function and I get the same issue with both of them. It is like the copy was a reference (or a pointer) instead of a proper copy. I am working with data records (classes) in Python, maybe it could be that.. I show you an example: >>> import copy >>> class player1: ... age = 23 ... score = 1 >>> class player2: ... age = 14 ... score =

问题 Could someone please offer a concise explanation for the difference between these two Python operations in terms of modifying the list? demo = ["a", "b", "c"] for d in demo: d = "" print demo #output: ['a', 'b', 'c'] for c in range(len(demo)): demo[c] = "" print demo #output: ['', '', ''] In other words, why doesn't the first iteration modify the list? Thanks! 回答1: The loop variable d is always a reference to an element of the iterable object. The question is not really a matter of when or