deep-copy | 易学教程

Copying an array of objects into another array in javascript

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How can I copy every element of an array (where the elements are objects), into another array, so that they are totally independent? I don't want changing an element in one array to affect the other. If the destination array doesn't exist yet... ...you can use slice() or concat() . slice() is probably more idiomatic (you'll also see slice(0) , but the default is 0, so...): var destinationArray = sourceArray.slice(); // Probably more idiomatic // or var destinationArray = sourceArray.concat(); As of ES2015 (aka ES6), there's also Array.from , which creates a new array from any array-like thing

Concisely deep copy a slice?

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问题 In Go, what's a concise/well-performing way to deep copy a slice? I need to copy the slice to a new backing array, because the other array is owned by something else and may be modified after the copy. I'm currently doing it like this: copy := append([]T{}, orig...) where T is the element type of orig . 回答1: Not sure which solution is fastest without a benchmark, but an alternative is using the built in copy : cpy := make([]T, len(orig)) copy(cpy, orig) From the documentation: func copy(dst,

python multiprocessing arguments: deep copy?

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问题 from multiprocessing import Process # c is a container p = Process(target = f, args = (c,)) p.start() I assume a deep copy of c is passed to function f because shallow copy would make no sense in the case of a new process (the new process doesn't have access to the data from the calling process). But how is this deep copy defined? There is a whole set of notes in the copy.deepcopy() documentation, do all these notes apply here as well? The multiprocessing documentation says nothing... 回答1:

How to create a Bitmap deep copy

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问题 I'm dealing with Bitmaps in my application and for some purposes I need to create a deep copy of the Bitmap. Is there an elegant way how to do it? I tried Bitmap deepCopy = original.Clone(); ,well apparently this doesn't create a deep copy, but shallow one. My next attempt was to create a new Bitmap Bitmap deepCopy = new Bitmap(original); Unfortunately this constructor is Bitmap(Image), not Bitmap(Bitmap) and Bitmap(Image) will convert my nice 8bppIndexed Pixelformat into a different one.

Java deep copy library

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问题 Is there library that can make deep copy? ex) normal object, array, list, inputstream etc. 回答1: @Konrad's posting is spot on. The only general way of doing deep copying is to use a Java serialization mechanism. Obviously, it is expensive. The other caveat is that some Java objects are impossible to copy by serialization. Examples include Thread and subclasses cannot be serialized because a thread's execution state cannot be serialized. Streams in general cannot be serialized because you

Python: RuntimeError: super-class init() of %S was never called

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I tried to do some operation ( setParent ) on an object in Python (an instance of a class which inherits from a different class - to be specific, QtGui.QLabel ), but during runtime the above error was raised. The object itself has had some fields with actual content (verified on debug), but from some reason I couldn't "use" it. What does the error mean and how can I fix it? For some additional information, I shall say that the object was returned from a static method before I tried to do this operation on it. The subclass has a __init__() function of its own: def __init__(self, image, father):

Deep copy of PHP array of references

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So $array is an array of which all elements are references. I want to append this array to another array called $results (in a loop), but since they are references, PHP copies the references and $results is full of identical elements. So far, the best working solution is: $results[] = unserialize(serialize($array)); which I fear to be incredibly inefficient. Is there a better way to do this? You can use the fact that functions dereferences results when returning, for exemple here $array_by_myclone will still have a reference to $original ( $array_by_myclone[0][0] == 'foo' ) while $array_by

“Deep copy” nested list without using the deepcopy function

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I am trying to copy the nested list a , but do not know how to do it without using the copy.deepcopy function. a = [[1, 2], [3, 4]] I used: b = a[:] and b = a[:][:] But they all turn out to be shallow copy. Any hints? My entry to simulate copy.deepcopy : def deepcopy(obj): if isinstance(obj, dict): return {deepcopy(key): deepcopy(value) for key, value in obj.items()} if hasattr(obj, '__iter__'): return type(obj)(deepcopy(item) for item in obj) return obj The strategy: iterate across each element of the passed-in object, recursively descending into elements that are also iterable and making new

In Javascript, when performing a deep copy, how do I avoid a cycle, due to a property being “this”?

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I have some library code that is cycling endlessly on me. I'm not clear on how to best perform cycle detection and avoidance in javascript. i.e. there's no programmatic way of inspecting whether an object came from a "this" reference, is there? Here's the code. Thanks! setAttrs: function(config) { var go = Kinetic.GlobalObject; var that = this; // set properties from config if(config !== undefined) { function setAttrs(obj, c) { for(var key in c) { var val = c[key]; /* * if property is an object, then add an empty object * to the node and then traverse */ if(go._isObject(val) && !go._isArray

How can I make a deep copy in Objective-C?

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I'm learning ios development and I'm confused with deep copying in Objective-C. For example,I have three class below. Now I want to deep copy ClassA, can anybody teach me to finish the copy method? A: @interface ClassA : NSObject <NSCopying> @property (nonatomic, assign) int aInt; @property (nonatomic, retain) ClassB *bClass; @end B: @interface ClassB : NSObject <NSCopying> @property (nonatomic, assign) int bInt; @property (nonatomic, retain) ClassC *cClass; @end C: @interface ClassC : NSObject <NSCopying> @property (nonatomic, assign) int cInt; @property (nonatomic, copy) NSString *str; @end