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Questions tagged [shallow-copy]

A shallow copy of an object is a duplicate that may not be fully independent of the original, in the sense that any references / pointers it holds to other objects refer to the same objects that the original's do. Use this tag for questions regarding implementing or using shallow copying methods.

Shallow copying is a process by which an object is duplicated to create a copy that may not be wholly independent of the original. Also known as "field by field" copying, this differs from deep copying with respect to the treatment of references / pointers to other objects: shallow copying copies the references / pointers held by the original, whereas deep copying makes a deep copy of each referenced object, too. Shallow copying is "shallow" in the sense that it copies only the original object itself, not any appearing deeper in its reference graph.

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What is the difference between a deep copy and a shallow copy?

What is the difference between a deep copy and a shallow copy?
David Locke
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How do I create a copy of an object in PHP?

It appears that in PHP objects are passed by reference. Even assignment operators do not appear to be creating a copy of the Object. Here's a simple, contrived proof: b = "after";…
Nick Stinemates
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Why and when to use angular.copy? (Deep Copy)

I've been saving all the data received from services direct to local variable, controller, or scope. What I suppose would be considered a shallow copy, is that correct? Example: DataService.callFunction() .then(function(response) { $scope.example…
Superman2971
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Shallow copy of a Map in Java

As I understand it, there are a couple of ways (maybe others as well) to create a shallow copy of a Map in Java: Map data = new HashMap(); Map shallowCopy; // first way shallowCopy = new…
dcp
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Fastest Way to do Shallow Copy in C#

I wonder what is the fastest way to do shallow copying in C#? I only know there are 2 ways to do shallow copy: MemberwiseClone Copy each field one by one (manual) I found that (2) is faster than (1). I'm wondering if there's another way to do…
tep
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How to clone or copy a set in Python?

For copying a list: shallow_copy_of_list = old_list[:]. For copying a dict: shallow_copy_of_dict = dict(old_dict). But for a set, I was worried that a similar thing wouldn't work, because saying new_set = set(old_set) would give a set of a set? But…
Evgeni Sergeev
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When should I pass or return a struct by value?

A struct can be either passed/returned by value or passed/returned by reference (via a pointer) in C. The general consensus seems to be that the former can be applied to small structs without penalty in most cases. See Is there any case for which…
Kaiting Chen
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Does Object.assign() create a deep copy or a shallow copy?

I just came across this concept of var copy = Object.assign({}, originalObject); which creates a copy of original object into the "copy" object. However, my question is, does this way of cloning object create a deep copy or a shallow copy? PS: The…
ShivangiBilora
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In Java, what is a shallow copy?

java.util.Calendar.clone() returns "...a new Calendar with the same properties" and returns "a shallow copy of this Calendar". This does not appear to be a shallow copy as answered here on SO. That question is tagged language-agnostic, Java does…
Will
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Default assignment operator= in c++ is a shallow copy?

Just a simple quick question which I couldn't find a solid answer to anywhere else. Is the default operator= just a shallow copy of all the class' members on the right hand side? Class foo { public: int a, b, c; }; foo f1, f2; ... f1 =…
Christopher Dorian
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Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it…
SmacL
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Python list slice syntax used for no obvious reason

I occasionally see the list slice syntax used in Python code like this: newList = oldList[:] Surely this is just the same as: newList = oldList Or am I missing something?
Charles Anderson
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Shallow copy or Deep copy?

I am a bit new to these two methods of copying one object into the other. I am confused and unable to spot out the major difference between deep copy and shallow copy.. I had gone through a lots of theory regarding this, but I need explanation with…
Srinivas Cheruku
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Object copy using spread syntax actually shallow or deep?

I understand spread syntax makes a shallow copy of objects, i.e., the cloned object refers to the same reference as the original object. However, the actual behaviour seems contradicting and confusing. const oldObj = {a: {b: 10}}; const newObj =…
richa Singh
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Shallow copy of a hashset

Whats the best way of doing it? var set2 = new HashSet(); Traverse the set with a foreach like this. foreach (var n in set) set2.Add(n); Or use something like union like this. set2 = set.UnionWith(set); // all the elements
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