pass-by-value

问题 How can I pass an integer by reference in Python? I want to modify the value of a variable that I am passing to the function. I have read that everything in Python is pass by value, but there has to be an easy trick. For example, in Java you could pass the reference types of Integer , Long , etc. How can I pass an integer into a function by reference? What are the best practices? 回答1: It doesn't quite work that way in Python. Python passes references to objects. Inside your function you have

问题 I\'m really new to Swift and I just read that classes are passed by reference and arrays/strings etc. are copied. Is the pass by reference the same way as in Objective-C or Java wherein you actually pass \"a\" reference or is it proper pass by reference? 回答1: Types of Things in Swift The rule is: Class instances are reference types (i.e. your reference to a class instance is effectively a pointer ) Functions are reference types Everything else is a value type ; "everything else" simply means

问题 I always thought Java was pass-by-reference . However, I\'ve seen a couple of blog posts (for example, this blog) that claim that it isn\'t. I don\'t think I understand the distinction they\'re making. What is the explanation? 回答1: Java is always pass-by-value . Unfortunately, when we pass the value of an object, we are passing the reference to it. This is confusing to beginners. It goes like this: public static void main(String[] args) { Dog aDog = new Dog("Max"); Dog oldDog = aDog; // we

问题 What is the difference between this 2 codes: Code A: Foo myFoo; myFoo = createfoo(); where public Foo createFoo() { Foo foo = new Foo(); return foo; } Vs. Code B: Foo myFoo; createFoo(myFoo); public void createFoo(Foo foo) { Foo f = new Foo(); foo = f; } Are there any differences between these 2 pieces of codes? 回答1: Java always passes arguments by value NOT by reference. Let me explain this through an example: public class Main { public static void main(String[] args) { Foo f = new Foo("f");

问题 class D { public static void main(String args[]) { Integer b2=128; Integer b3=128; System.out.println(b2==b3); } } Output: false class D { public static void main(String args[]) { Integer b2=127; Integer b3=127; System.out.println(b2==b3); } } Output: true Note: Numbers between -128 and 127 are true. 回答1: When you compile a number literal in Java and assign it to a Integer (capital I ) the compiler emits: Integer b2 =Integer.valueOf(127) This line of code is also generated when you use

问题 Is it better in C++ to pass by value or pass by constant reference? I am wondering which is better practice. I realize that pass by constant reference should provide for better performance in the program because you are not making a copy of the variable. 回答1: It used to be generally recommended best practice 1 to use pass by const ref for all types , except for builtin types ( char , int , double , etc.), for iterators and for function objects (lambdas, classes deriving from std::*_function )

问题 So, I have some code, kind of like the following, to add a struct to a list of structs: void barPush(BarList * list,Bar * bar) { // if there is no move to add, then we are done if (bar == NULL) return;//EMPTY_LIST; // allocate space for the new node BarList * newNode = malloc(sizeof(BarList)); // assign the right values newNode->val = bar; newNode->nextBar = list; // and set list to be equal to the new head of the list list = newNode; // This line works, but list only changes inside of this

问题 The primitive types (number, string, etc.) are passed by value, but objects are unknown, because they can be both passed-by-value (in case we consider that a variable holding an object is in fact a reference to the object) and passed-by-reference (when we consider that the variable to the object holds the object itself). Although it doesn\'t really matter at the end, I want to know what is the correct way to present the arguments passing conventions. Is there an excerpt from JavaScript

问题 In C#, I have always thought that non-primitive variables were passed by reference and primitive values passed by value. So when passing to a method any non-primitive object, anything done to the object in the method would effect the object being passed. (C# 101 stuff) However, I have noticed that when I pass a System.Drawing.Image object, that this does not seem to be the case? If I pass a system.drawing.image object to another method, and load an image onto that object, then let that method

问题 This question already has answers here : Is JavaScript a pass-by-reference or pass-by-value language? (30 answers) Closed 5 years ago . I\'m looking for some good comprehensive reading material on when Javascript passes something by value and when by reference and when modifying a passed item affects the value outside a function and when not. I\'m also interested in when assigning to another variable is by reference vs. by value and whether that follows any different rules than passing as a