new-operator

Is there any reason to manually `return` in a constructor function?

由 好久不见. 提交于 2019-12-07 12:48:19
问题 Typically, in a constructor function, the object that is bound to this within the function is returned by it when it is called with the new prefix. But I would imagine that it's also possible (I think I even read this in crockford's book) to manually return your own value. Are there any places where such a practice is useful? 回答1: If you return a value type from the constructor, you'll get different behavior depending on if new was used. That's how String works. Look at this object in your

Creating array of pointers to class object

由 假装没事ソ 提交于 2019-12-07 09:23:00
问题 Question: Create an array of at least four pointers to Reader objects. Use the New operator to create at least four pointers to derived class objects and assign them to the array. I'm not sure If I did it right or not. Reader is the base class. John, David, Daniel, Mark are the derived class int main(void) { Reader *obj[4]; obj[0] = new John(); obj[1] = new David(); obj[3] = new Daniel(); obj[2] = new Mark(); } Would this be right??? 回答1: Your code is correct . And as @sharptooth suggested,

How to create new File txt by using Adobe Air

由 谁说我不能喝 提交于 2019-12-07 09:13:28
I want to ask how to create new file with adobe air so i can write it..... And how to put it in our current project? I have seen so many resource, but they used existed file that created manually and only update it content... Thanks Alot everything is explained (with sample code) in the documentation: flash.filesystem.FileStream flash.filesystem.File Reading and writing files (Adobe AIR 1.0 and later) private var fileReferenceSave:FileReference= new FileReference(); private function onSaveText():void { fileReference.save(myText.text,"myText.txt"); } 来源： https://stackoverflow.com/questions

create new application ruby on rails

由 穿精又带淫゛_ 提交于 2019-12-07 09:10:03
问题 I'm bit confused by "easy" working with ruby on rails, cause I already spend three days by trying create an app. I work on site5 hosting, and try to create new app. step by step: $ rails new app -d mysql $ gem install mysql $ gem install mysql2 and after $ rake db:create it report about error Could not find gem 'mysql2 (~> 0.2.6, runtime)' in any of the gem sources listed in your Gemfile. I google it, but still can't fix problem. Can anybody help? 回答1: Running rails new app -d mysql will

React/RCTBridgeDelegate.h' file not found

由 你。 提交于 2019-12-07 07:51:18
问题 I have created a new project called auth using react-native init auth at terminal.When i tried to run the project using react-native run-ios. The build failed and gave a error 'React/RCTBridgeDelegate.h' file not found. Tried to update the react native version react-native run-ios at terminal in mac I expect the build to be successful and see the ios simulator The actual result which i got is build failed and hence cant see the simulator 回答1: The issue is related to cocoapods dependency

how do you delete an object allocated with placement new

由 感情迁移 提交于 2019-12-07 07:09:51
问题 there are quite a few faces for the new operator in c++, but I'm interested in placement new. Suppose you allocate memory at a specific memory location int memoryPool[poolSize*sizeof(int)]; int* p = new (mem) int; //allocates memory inside the memoryPool buffer delete p; //segmentation fault How can I correctly deallocate memory in this case? What if instead of built-in type int I would use some class called myClass? myClass memoryPool[poolSize*sizeof(myClass )]; myClass * p = new (mem)

Is it possible to create a function pointer to the a function's `new` operator/constructor?

由 僤鯓⒐⒋嵵緔 提交于 2019-12-07 06:14:02
问题 If I were to wanted to parameterize creating an object, I could of course make a function which called new on a particular class and passed out a pointer. I am wondering if it's possible to skip that step and pass a function pointer to the new operator itself. 回答1: boost::lambda provides function wrappers for new and delete. These can be used to easily convert an new call into a function object. 回答2: operator new (as well as the other flavours) takes care of allocating memory but does not

boost::make_shared is not calling (placement) operator new?

由 不羁的心 提交于 2019-12-07 03:09:49
问题 I am using boost::make_shared for the first time to create objects pointed to by shared pointers. Mainly because our code was too slow and the single allocation really helped to improve performance. After fixing some memory leaks "the hard manual way" I decided to implement a simple memory leak detector by overriding new operators for all relevant classes just for counting which objects are still alive at specific points in our application. I have implemented this several times before and was

Overriding operator new/delete in derived class

由 江枫思渺然 提交于 2019-12-07 02:18:10
问题 I have a stateless, abstract base class from which various concrete classes inherit. Some of these derived classes are stateless as well. Because many of them are created during a run, I'd like to save memory and overhead by having all stateless derived classes emulate a singleton, by overriding operator new()/delete(). A simplified example would look something like this: #include <memory> struct Base { virtual ~Base() {} protected: Base() {} // prevent concrete Base objects }; struct D1 :

Operator new in C# vs C++

由 醉酒当歌 提交于 2019-12-07 00:58:51
问题 Coming from C++, I am confused as to the use of the new keyword in C#. I understand that it doesn't work like C++'s new in the sense that you do not have to manually control the lifetime of the object, as C# has garbage collection. However, when reading over other peoples C# code I notice statements like in code snippet 1. Wouldn't it be far easier to avoid the use of new altogether, like in code snippet 2? Snippet 1 Foo fooInstance = new Foo(); Snippet 2 Foo fooInstance; My question is, what
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