Question

有没有办法用schema.liczby之类的内容替换schema.studenci和schema.($variable)？在这种情况下，避免重复代码执行相同的操作只会针对不同的结构。

string getFieldType(string field_name, SCHEMA schema, string table)
{
    if (table == "liczby")
    {
        for (int i = 0; i < schema.liczby.integers.size(); i++)
        {
            if (schema.liczby.integers[i] == field_name)
            {
                return "int";
            }
        }

        for (int i = 0; i < schema.liczby.strings.size(); i++)
        {
            if (schema.liczby.strings[i] == field_name)
            {
                return "string";
            }
        }

        for (int i = 0; i < schema.liczby.doubles.size(); i++)
        {
            if (schema.liczby.doubles[i] == field_name)
            {
                return "double";
            }
        }

        for (int i = 0; i < schema.liczby.booleans.size(); i++)
        {
            if (schema.liczby.booleans[i] == field_name)
            {
                return "double";
            }
        }
    }
    else if (table == "studenci")
    {
        for (int i = 0; i < schema.studenci.integers.size(); i++)
        {
            if (schema.studenci.integers[i] == field_name)
            {
                return "int";
            }
        }

        for (int i = 0; i < schema.studenci.strings.size(); i++)
        {
            if (schema.studenci.strings[i] == field_name)
            {
                return "string";
            }
        }

        for (int i = 0; i < schema.studenci.doubles.size(); i++)
        {
            if (schema.studenci.doubles[i] == field_name)
            {
                return "double";
            }
        }

        for (int i = 0; i < schema.studenci.booleans.size(); i++)
        {
            if (schema.studenci.booleans[i] == field_name)
            {
                return "double";
            }
        }
    }
}

Answer 1

我们可以重构您的代码。有很多方法可以给这只猫上皮。我认为std::map让事情变得非常简单，但是YMMV。我认为你应该改变第二个地图的类型，这样你就可以存储类型+值（boost:variant或者多态设置可能会很好用。）这段代码只是一个起点。

#include <string>
#include <map>
#include <vector>

typedef std::map<std::string, std::map<std::string, std::string>> SCHEMA;

int main() {
    SCHEMA schema;

    // Schema table
    schema["liczby"]["wartosc"] = "column";
    schema["liczby"]["wartość"] = "int";
    schema["studenci"]["indeks"] = "column";
    schema["studenci"]["imie"] = "column";
    schema["studenci"]["nazwisko"] = "column";
    schema["przedmioty"]["id"] = "column";
    schema["przedmioty"]["nazwa"] = "column";
    schema["przedmioty"]["semestr"] = "column";
    schema["sale"]["nazwa"] = "column";
    schema["sale"]["rozmiar"] = "column";
    schema["sale"]["projektor"] = "column";
    schema["sale"]["powierzchnia"] = "column";
}

std::string getFieldType(std::string field_name, SCHEMA& schema, std::string table) {
    return schema[table][field_name];
}

Answer 2

没问题。您的LICZBY_SCHEMA，STUDENCI_SCHEMA，PRZEDMIOTY_SCHEMA和SALE_SCHEMA相同，因此我们将其全部替换为BASIC_SCHEMA。然后代码变得更加简单：

struct BASIC_SCHEMA
{
  vector<string> columns;
  vector<string> integers;
  vector<string> strings;
  vector<string> booleans;
  vector<string> doubles;
};

struct SCHEMA
{
  BASIC_SCHEMA liczby;
  BASIC_SCHEMA studenci;
  BASIC_SCHEMA przedmioty;
  BASIC_SCHEMA sale;
};

string getFieldType(string field_name, SCHEMA schema, string table)
{
  BASIC_SCHEMA subSchema;

  if (table == "liczby")
    subSchema = schema.liczby;
  else if (table == "studenci")
    subSchema = schema.studenci;
  else
    return("");

  for (unsigned int i = 0; i < subSchema.integers.size(); i++)
    {
      if (subSchema.integers[i] == field_name)
        {
          return "int";
        }
    }
  ...
 }

我们可以使它更简洁，例如find(...)，但这是另一个故事。

用变量替换结构成员名称

2 个答案: