static_downcast

C++ Grammar
  • static_castは何をしているか分からないので駄目である
  • そこで実行時にチェックできる場合はチェックするdowncast (実装)
    • VC++7.1のバグのおかげですごく苦労した
  • cv-qualifierは自動なのがミソ

[]#include[] []<pstade/static_downcast.hpp>[]

[]#include[] []<boost/utility/result_of.hpp>[]




[]using[] []namespace[] []pstade[][];[]
[]struct[] []base[]

[]{[]

[]};[]
[]struct[] []derived[][] : [][]base[]

[]{[]

    []derived[][]() { }[]

    []void[] []foo[][]() [][]const[][] { }[]

[]};[]
[]int[] []main[][]()[]

[]{[]

    []derived[] []const[] []D[][];[]

    []base[] []const[][]& [][]crB[][] = [][]D[][];[]
    []boost[][]::[][]result_of[][]<[]

        []op_static_downcast[][]<[][]derived[][]>([][]base[] []const[][]&)[]

[]    >::[][]type[] []d[][] = [][]pstade[][]::[][]static_downcast[][]<[][]derived[][]>([][]crB[][]);[]
    []pstade[][]::[][]static_downcast[][]<[][]derived[][]>([][]crB[][]).[][]foo[][]();[]

[]}[]