casting

问题 I come from a background of C# and Java and I can't seem to understand what casting with pointers means in C++. For example: int x = 1; char c = *((char*)&x); What does it do? What it is useful for? 回答1: In both your examples you're making mistakes making the code not compile. So I'll assume you're trying to do the following: int x = 1; char c = *((char*)&x); Depending on your architecture, c will now have either the value of the least or the most significant byte of x . In this example this

问题 Calling a .net SOAP1.1 web service from android using ksoap2 lib I met a problem of casting response to a custom object. For instance the code below is called correct after httpTransport.call(soapAction, soapEnvelope); and have data inside. But I cant't cast it to specific object neither to SoapObject or Vector as I saw in several examples, I get CastException or simple nothing. If somebody knows how to deal with it, please help. public StatusSetting[] GetAllStatuses(String installation){

问题 The reinterpret_cast as we know can cast any pointer type to any another pointer type. The question I want to ask regarding this cast operator are: How does reinterpret_cast work, What is the magic(the internal implementation) that allows reinterpret_cast to work? How to ensure safety when using reinterpret_cast ? As far as i know, it doesn't guarantee of safe casting, So what precaution to take while using reinterpret_cast? What is the practical usage of this operator. I have not really

问题 The reinterpret_cast as we know can cast any pointer type to any another pointer type. The question I want to ask regarding this cast operator are: How does reinterpret_cast work, What is the magic(the internal implementation) that allows reinterpret_cast to work? How to ensure safety when using reinterpret_cast ? As far as i know, it doesn't guarantee of safe casting, So what precaution to take while using reinterpret_cast? What is the practical usage of this operator. I have not really

问题 I have a class with implements 2 interfaces and inherits 1 class. So, generally it looks like this: class T : public A, public IB, public IC { }; There is one point in the code where I have an IB * , but could really use an A * . I was hoping that a dynamic cast would like this: IB *b_ptr = new T; // it's really more complicated, but serves the example A *a_ptr = dynamic_cast<A *>(b_ptr); unfortunately, this doesn't work. Is there a proper way to do this? Or should I implement a work around?

问题 I have such matrix in my program: double m[3][4] = { {2, 4, 5, 7}, {4, 5, 1, 12}, {9, 12, 13, -4} }; And I'd like to cast it to double** type. I've already tried simple double** a = (double**)m; , but it doesn't work (when I try to read any value, I get "Access violation reading location 0x00000000.", which means I'm trying to read from NULL adress. I found almost working solution: double *b = &m[0][0]; double **c = &b; It works when I read field c[0][any] But same NULL adress reading problem

问题 I have this XML document <AdditionalParameters> <PublishToPdf Type ="System.Boolean">False</PublishToPdf> </AdditionalParameters> in my code and I'm trying to build an array of arguments containing the <PublishToPdf> node. object test = (object) ((typeof(publishNode.Attributes["Type"].value)) publishNode.InnerText); This breaks at compile time of course. I can't figure out how to cast the publishNode.InnerText('false') to a runtime defined object of type specified in the XML file and store it

问题 I'm working with indexeddb and typescript. My issue is that TS doesn't seem to be able handle the event.target.result property. Case in point: request.onsuccess = (event) => { namespace.db = event.target.result; //the property 'results' does not //exist on the value of type 'EventTarget' var a = event.target; var b = <IDBOpenDBRequest>a; var c = b.result; // <-- magically there's a results property here version = parseInt(namespace.db.version); console.log("version: " + version); deferred

问题 From the standard (4.7) it looks like the conversion from int to unsigned int, when they both use the same number of bits, is purely conceptual: If the destination type is unsigned, the resulting value is the least unsigned integer congruent to the source integer (modulo 2 n where n is the number of bits used to represent the unsigned type). [ Note: In a two’s complement representation, this conversion is conceptual and there is no change in the bit pattern (if there is no truncation). — end

问题 I have an array of type object which are strings. I would like to convert them to strings. What would be the quickest way of doing so? Eg.: I have this object[] and want to convert it so it is this string[] . UPDATE: I think the problem is that some of the objects on the object[] are actually other objects like integers. I would need to convert them to strings first. Please include that into your solution. Thanks. 回答1: Probably not the most efficient way to do it...it has the benefit of