Question

When I write code like this in VS 2008:

.h struct Patterns {         string ptCreate;         string ptDelete;         string ptDrop;         string ptUpdate;         string ptInsert;         string ptSelect;     };       class QueryValidate {     string query;     string pattern;     static Patterns pts; public:     friend class Query;     QueryValidate(const string& qr, const string& ptn):       query(qr), pattern(ptn) {}     bool validate() {         boost::regex rg(pattern);         return boost::regex_match(query, rg);     }     virtual ~QueryValidate() {} }; 

I then initialize my structure like this:

.cpp string QueryValidate::pts::ptCreate = 'something'; string QueryValidate::pts::ptDelete = 'something'; //... 

The compiler gives the following errors:

‘Patterns’: the symbol to the left of a ‘::’ must be a type ‘ptSelect’ : is not a member of ‘QueryValidate’

What am I doing wrong? Is this a problem with Visual Studio or with my code? I know that static members except for const ones must be defined outside the class they were declared in.

Answer 1

You’re trying to create a non-static member (ptCreate) of a static member (pts). This won’t work like this.

You got two options, either use a struct initializer list for the Patterns class.

Patterns QueryValidate::pts = {'CREATE', 'DELETE'}; // etc. for every string 

Or, much safer (and better in my opinion), provide a constructor in Patterns and call that one.

struct Patterns {    Patterns() { /*...*/ }    /* ... */ } 

On a side not, your code wouldn’t work in any C++ compiler, it’s not a conflict with Visual Studio things.