deep-copy

问题 I have an object with properties that are NSString, UIImageView and simple vars like BOOL, int and float. I'm trying to create a deep copy of the object. For that I've implemented the NSCopying protocol to my class and the copyWithZone method like: -(id)copyWithZone:(NSZone *)zone { iItem *clone = [[iItem alloc] init]; //iItem *clone = [super copyWithZone:zone]; clone.originalTransform = self.originalTransform; clone.initialTransform = self.initialTransform; clone.originalFrame = self

问题 I have a persistent entity that I'm using as a template: Company Locations Departments Employees In other words, a Company contains many Locations , which contains many Departments , which contains many Employees . I have one Company set up as a template that should be copied when a new company is created. However, this template is persistent in the database. I tried using the following code to deep clone it: var template = EntityLoadByPK("Company", 13); var company = Duplicate(template);

问题 This question already has answers here : How to clone or copy a list? (16 answers) Copying nested lists in Python (3 answers) Closed last year . To understand why I was getting an error in a program , in which I tried to find the "minor" of a determinant, I wrote a simpler program because my variables were messed up. This function below takes in a 2 * 2 matrix as an input, and returns a list containing its rows (pointless and inefficient, I know, but I'm trying to understand the theory behind

问题 Is python's copy module thread safe? If not, how should I copy\deepcopy mutable objects in a thread-safe manner in python? 回答1: Python's GIL protects bytecodes, not Python statements (see short or long explanations). As both copy.copy() and copy.deepcopy() are implemented in python, they are certainly more than a single bytecode, so no, they are not thread safe! If you must work with multiple threads, and there are many cases you should such as having IO dedicated threads, do what must be

问题 I have a class called Heap that is a Vector of pointers to HeapItem objects vector<HeapItem*> myHeap; I want to create a deep copy of Heap so that I can delete all the items in the copy without affecting the original Heap. EX: OriginalHeap = new Heap(); OriginalHeap.Insert(HeapItem1); OriginalHeap.Insert(HeapItem2); OriginalHeap.Insert(HeapItem3); CopyHeap = OriginalHeap; CopyHeap.deleteMin(); print(OriginalHeap); print(CopyHeap); Output: OriginalHeap = HeapItem1,HeapItem2,HeapItem3 CopyHeap

问题 Concerning lazy copying: Will Matlab ever copy data passed to a mexFunction, which modifies it? For instance in myMex(input1(:,:,ii), input2(:,:,ii)) can one be sure, that the input matrices are never copied, so that one can pass something in and modify it, without having to return a reference? 回答1: In certain cases, MATLAB implements some optimizations to avoid copying data when calling functions. With MEX-functions, the input as passed as const mxArray *prhs[] ( prhs is an array of pointers

问题 My objective is to do a deep copy of a class, but a virtual class is causing trouble. #include<iostream> using namespace std; class Vir//pure virtual class { public: virtual void hi()=0; }; class Handler:public Vir { public: int i; Handler() {} Handler(int val):i(val) {} void hi() {cout<<"Value of i="<<i<<endl;} int getI() const {return i;} void setI(int j) {i=j;} }; class ControlPanel { public: Vir *v; ControlPanel(const ControlPanel& c)//copy constructor { v=new Handler; v->setI(c.getI());

问题 At first I thought arr.slice(0) was doing a deep unreferenced copy, but it is actually doing just a shallow unreferenced copy, so if the array contains nested arrays, they are still referenced: var a = [1,2] var b = [3,4] var c = [a,b] var d = c.slice(0) d[0] === a // true, which means it is the /same/ object d[0][0] = "Hi!" a // ["Hi!", 2] (example source) The solution on the links provided is fairly easy when you know the structure of the array (just .slice(0) ing again the nested arrays

问题 I'm trying to improve the speed of an algorithm and, after looking at which operations are being called, I'm having difficulty pinning down exactly what's slowing things up. I'm wondering if Python's deepcopy() could possibly be the culprit or if I should look a little further into my own code. 回答1: Looking at the code (you can too), it goes through every object in the tree of referenced objects (e.g. dict's keys and values, object member variables, ...) and does two things for them: see if

问题 I'm attempting to perform a deep copy of the following struct: // Ternary Tree type Tree struct { Left *Tree Mid *Tree Right *Tree Value interface{} Parent *Tree Orientation string IsTerminal bool Type string } The following is my sorry attempt. It looks like I'm creating a new tree at the root but it's children are still pointing to the same address in memory. func (tree *Tree) CopyTree() *Tree { if (tree == nil) { return nil } else { copiedTree := &Tree { tree.Left.CopyTree(), tree.Mid