declaration

问题 With new Xcode 8.3, I get error : Cannot override a non-dynamic class declaration from an extension in line of code override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell How I can avoid this warning? 回答1: which means, you can't not override like super class delegate method in extension. the way you can do is mv extension override method to subclass declare. final class DEMO, UITableViewDataSource, UITableViewDelegate { override func tableView(

问题 Can I write simply for (int i = 0; ... instead of int i; for (i = 0; ... in C or C++? (And will variable i be accessible inside the loop only?) 回答1: Its valid in C++ It was not legal in the original version of C. But was adopted as part of C in C99 (when some C++ features were sort of back ported to C) Using gcc gcc -std=c99 <file>.c The variable is valid inside the for statement and the statement that is looped over. If this is a block statement then it is valid for the whole of the block.

问题 I am currently teaching a colleague .Net and he asked me a question that stumped me. Why do we have to declare? if var is implicit typing, why do we have to even declare? Animal animal = new Animal(); becomes var animal = new Animal(); could become animal = new Animal(); The implicit typing would still mean that this is a statically typed variable. If two different types are assigned to the variable, if they do not share a base class, (other than object), that could be a compiler error. Is

问题 When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: ===IBM Member Specialization Example=== template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>:

问题 I have been investigating when it is possible to mix variables declared with extern , static and no storage specifier in global scope. The results have left me quite confused. This is what I found (each paragraph is a separate compilation unit): /* ok */ int x; int x; /* ok */ int f(); int f(); /* ok */ int x; extern int x; /* ok */ int f(); extern int f(); /* error: static declaration follows non-static declaration */ int x; static int x; /* ok (no warning) */ int f(); static int f(); /* ok

问题 I'm asking which is the best practice between this two implementation: for ( int i = 0; i < 5; i++ ) for ( int j = 0; j < 5; j++ ) ...some code here... ...other code... for ( int i = 0; i < 5; i++ ) for ( int j = 0; j < 5; j++ ) ...some code here... or this one: beginning of function/main int i,j; ...some code... for ( i = 0; i < 5; i++ ) for ( j = 0; j < 5; j++ ) ...some code here... ...other code... for ( i = 0; i < 5; i++ ) for ( j = 0; j < 5; j++ ) ...some code here... In other words is

问题 I know when we want to assign values to 2D arrays as we declare the array, we do this: int myArray[2][4] = {{1,2,3,4},{5,6,7,8}}; But how should I assign values "after" declaring it? I want to do something like this: int myArray[2][4]; myArray = {{1,2,3,4},{5,6,7,8}}; When I do it, the compiler gives error. Help please. 回答1: If you want to use std::vector then you can do this: #include <vector> int main() { std::vector< std::vector<int> > arrV ; arrV = { {1,2,3,4}, {5,6,7,8} }; } or using std

问题 Until today, I thought that the following two notations are the same (edit: Dim was replaced by Property ) Property arrayVariable() As Object Property arrayVariable As Object() Today I found that former one throws error Option Strict On disallows late binding. while the latter compiles OK in expression dictionary1.TryGetValue(CStr(arrayVariable(0)), result) . Please what is the difference between them? I would always use the second notation if it also allowed to specify the array dimensions.

问题 char(*p)[15]; char(*p)(int *a); int(*pt)(char*); int *pt(char*); anyone help? 回答1: Basic rule: Start at the identifier and read right when you can, left when you must. Start at the identifier*. Say it, followed by "is a". Put your "left foot" one character to the left of it. Read rightwards until you hit the end or a ) . Put your "right foot" one character to the right of where that ) is, if that's what you hit. If you see [42] as you read rightwards, say "array of 42". If you see a ( as you

问题 I'm trying to declare a list of lists in this way: List_vector<List_vector<int> > multilist; But Eclipse underlines the above declaration and gives this error: required from here Partial List_vector implementation: template<class T> class List_vector: public Linear_list<T, int> { public: typedef typename Linear_list<T, int>::value_type value_type; typedef typename Linear_list<T, int>::position position; List_vector(); List_vector(int); List_vector(const List_vector<T>&); ~List_vector();