deep-copy | 易学教程

Cloning a record in rails, is it possible to clone associations and deep copy?

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问题 I'm .clone -ing a record in rails... new_blerg = Blerg.find(1).clone This record has loads and loads of associations, and those associations even have associations. Is there a way to deep-copy a record and clone it so it is cloned with all of those associations too? 回答1: You may get some good use out of the Amoeba gem for ActiveRecord 3.2. It supports easy and automatic recursive duplication of has_one , has_many and has_and_belongs_to_many associations, field preprocessing and a highly

How to deep copy an irregular 2D array

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问题 How can I deep copy an irregularly shaped 2D array in Java? Ie. int[][] nums = {{5}, {9,4}, {1,7,8}, {8,3,2,10}} I'm unable to use Arrays.arrayCopy() for some reason (versioning?) 回答1: int[][] copy = new int[nums.length][]; for (int i = 0; i < nums.length; i++) { copy[i] = new int[nums[i].length]; for (int j = 0; j < nums[i].length; j++) { copy[i][j] = nums[i][j]; } } You can replace the second loop with System.arraycopy() or Arrays.copyOf(). 回答2: I wrote this in Eclipse, tested it, came back

“Deep copy” nested list without using the deepcopy function

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问题 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? 回答1: 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

How to deep copy 2 dimensional array (different row sizes)

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问题 This is my first question in a community like this, so my format in question may not be very good sorry for that in the first place. Now that my problem is I want to deep copy a 2 dimension array in Java. It is pretty easy when doin it in 1 dimension or even 2 dimension array with fixed size of rows and columns. My main problem is I cannot make an initialization for the second array I try to copy such as: int[][] copyArray = new int[row][column] Because the row size is not fixed and changes

Deep copy of dictionaries gives Analyze error in Xcode 4.2

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I have the following method in a NSDictionary category, to do a deep copy, which works fine. I just upgraded from Xcode 4.1 to 4.2, and the Analyze function gives two analyzer warnings for this code, as indicated: - (id)deepCopy; { id dict = [[NSMutableDictionary alloc] init]; id copy; for (id key in self) { id object = [self objectForKey:key]; if ([object respondsToSelector:@selector(deepCopy)]) copy = [object deepCopy]; else copy = [object copy]; [dict setObject:copy forKey:key]; // Both -deepCopy and -copy retain the object, and so does -setObject:forKey:, so need to -release: [copy release

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

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问题 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 :

C++: Deep copying a Base class pointer

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问题 I searched around and seems in order to perform this I need to change my Base class and want to know if this is the best approach. For example, I have a Base class: class Base {} Then a long line of derived classes: class Derived_1:: public Base {} class Derived_2:: public Derived_1{} ... ... class Derived_n:: public Derived_M{} And then I have another class: class DeepCopy { Base * basePtr; public: DeepCopy(DeepCopy & dc) {} } Assuming the Base class and Derived_x class copy constructors are

how to do true deep copy for NSArray and NSDictionary with have nested arrays/dictionary?

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Question: Is there a way to use existing objective-c methods to do a full deep copy of a NSDictionary or NSArray, that themselves have nested dictionaries or arrays within them? That is I have read the problem may be when it hits a nested dictionary or array it only copies the pointer to the nested item, and not copy the item truely. Background: So as an example for me I'm trying to load/save the following config with NSUserDefaults and when loading need to convert the immutable copies one gets from NSUserDefault to mutable prior to making changes. Items ( NSDictionary ) Item ( NSDictionary )

Java HashMap - deep copy

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问题 I am just trying to find out the best solution how to make a deep copy of HashMap . There are no objects in this map which implement Cloneable . I would like to find better solution than serialization and deserialization. 回答1: Take a look at Deep Cloning , on Google Code you can find a library. You can read it on https://github.com/kostaskougios/cloning. How it works is easy. This can clone any object, and the object doesnt have to implement any interfaces, like serializable. Cloner cloner =

How to make a deep copy of Java ArrayList [duplicate]

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Possible Duplicate: How to clone ArrayList and also clone its contents? trying to make a copy of an ArrayList. The underlying object is simple containing on Strings, ints, BigDecimals, Dates and DateTime object. How can I ensure that the modifications made to new ArrayList are not reflected in the old ArrayList? Person morts = new Person("whateva"); List<Person> oldList = new ArrayList<Person>(); oldList.add(morts); oldList.get(0).setName("Mortimer"); List<Person> newList = new ArrayList<Person>(); newList.addAll(oldList); newList.get(0).setName("Rupert"); System.out.println("oldName : " +