Roslyn+T4+EnvDTE项目完全自动化(3) ——生成c++代码

C++语法复杂，写一个示例通过T4可生成c++代码

需求：数据库，生成c++增，删，改，查代码

1. 数据库生成c++类，包含所有字段
2. 自动识别数据的主键Key
3. 查询生成赋值类字段，类型转换
4. 通过类自动生成sql的where条件
5. 类改变一些字段值，自动生成update sql
6. 生成所有字段打印代码

class Actor_Entry;      //数据库实体类
class Actor_UpdateEntry;//更新实体类
class Actor             //实体增，删，改，查类
{
public:
    bool Select(MYSQL* connect, const std::string& sql, std::vector& out);
    bool SelectAll(MYSQL* connect, std::vector& v);
    bool Update(MYSQL* connect, const Actor_UpdateEntry& set, const Actor_UpdateEntry& where, const std::string& whereSql);
    bool Update(MYSQL* connect, const std::string& whereSql);
    bool Insert(MYSQL* connect, Actor_UpdateEntry& v);
    bool Delete(MYSQL* connect, const Actor_UpdateEntry& v);
};
class Actor_Entry
{
public:
    std::string ToString();
    static Actor_Entry& New();//方便拷贝代码
    short int GetKey() const;
    // 数据字段，及类型映射
    // 主键（自动识别主键）
    short int Actor_Id;
    std::string First_Name;
    std::string Last_Name;
    std::string Last_Update;
};
//字段发生改变，自动生成sql
class Actor_UpdateEntry : public Actor_Entry
{
public:
    Actor_UpdateEntry(); 
    static Actor_UpdateEntry& New();//方便拷贝代码
    bool IsModified() const;
    void ResetModified();
    void Set_Actor_Id(const short int value);
    bool Actor_Id_Modified;

    void Set_First_Name(const std::string& value);
    bool First_Name_Modified;

    void Set_Last_Name(const std::string& value);
    bool Last_Name_Modified;

    void Set_Last_Update(const std::string& value);
    bool Last_Update_Modified;
};

一个数据库，不到10s生成7000+行代码

 实现方式：

读取表结构：

        public static IEnumerable GetTableSchemaEnumerable(MySqlConnectionStringBuilder builder)
        {
            using (var conn = GetConnection(builder))
            {
                var sql =
                    $"SELECT DISTINCT t.`TABLE_COMMENT`, c.* FROM information_schema.`COLUMNS` as c INNER join INFORMATION_SCHEMA.`TABLES` t on c.`TABLE_NAME`= t.`TABLE_NAME`  where c.TABLE_SCHEMA = '{builder.Database}';";

                using (var cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;

                    using (var reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            var obj = new TABLE_SCHEMA_();
                            obj.TABLE_COMMENT = reader[nameof(obj.TABLE_COMMENT)].DbCast();
                            obj.TABLE_NAME = reader[nameof(obj.TABLE_NAME)].DbCast();
                            obj.TABLE_CATALOG = reader[nameof(obj.TABLE_CATALOG)];
                            obj.TABLE_SCHEMA = reader[nameof(obj.TABLE_SCHEMA)];
                            obj.TABLE_NAME = reader[nameof(obj.TABLE_NAME)].DbCast();
                            obj.COLUMN_NAME = reader[nameof(obj.COLUMN_NAME)].DbCast();
                            obj.ORDINAL_POSITION = reader[nameof(obj.ORDINAL_POSITION)].DbCast();
                            obj.COLUMN_DEFAULT = reader[nameof(obj.COLUMN_DEFAULT)];
                            {
                                var v = reader[nameof(obj.IS_NULLABLE)];
                                obj.IS_NULLABLE = "Yes".EqualsByIgnoreCaseEx(v.DbCast());
                            }
                            obj.DATA_TYPE = reader[nameof(obj.DATA_TYPE)].DbCast();
                            obj.CHARACTER_MAXIMUM_LENGTH = reader[nameof(obj.CHARACTER_MAXIMUM_LENGTH)].DbCast();
                            obj.CHARACTER_OCTET_LENGTH = reader[nameof(obj.CHARACTER_OCTET_LENGTH)].DbCast();
                            obj.NUMERIC_PRECISION = reader[nameof(obj.NUMERIC_PRECISION)];
                            obj.NUMERIC_SCALE = reader[nameof(obj.NUMERIC_SCALE)];
                            obj.DATETIME_PRECISION = reader[nameof(obj.DATETIME_PRECISION)];
                            obj.CHARACTER_SET_NAME = reader[nameof(obj.CHARACTER_SET_NAME)].DbCast();
                            obj.COLLATION_NAME = reader[nameof(obj.COLLATION_NAME)].DbCast();
                            obj.COLUMN_TYPE = reader[nameof(obj.COLUMN_TYPE)].DbCast();
                            obj.COLUMN_KEY = reader[nameof(obj.COLUMN_KEY)].DbCast();
                            obj.EXTRA = reader[nameof(obj.EXTRA)];
                            obj.PRIVILEGES = reader[nameof(obj.PRIVILEGES)];
                            obj.COLUMN_COMMENT = reader[nameof(obj.COLUMN_COMMENT)].DbCast();
                            obj.GENERATION_EXPRESSION = reader[nameof(obj.GENERATION_EXPRESSION)];
                            obj.SRS_ID = reader[nameof(obj.SRS_ID)];
                            yield return obj;
                        }
                    }
                }
            }
        }

用t4生成c++代码：

bool <#= className #>::Insert(MYSQL* connect, <#= tab.ClassName_UpdateEntry #>& v)
{
    if(!v.IsModified())
    {
        return false;
    }
	std::string f;
	std::string values;
<#+
    var isOneKey = tab.Keys.Length == 1;//判断是不是单主键
    foreach (var field in tab.FieldsSupported)
    {
        var type = field.Type;
        var name = field.Name;
#>
    if (v.<#=field.NameModify#>)
    {
	    f += " `<#=field.ColumnName#>`,";
	    values += std::format(" '{}',", v.<#=field.Name#>);
    }
<#+
	}
#>
<#+if(isOneKey){//自增主键，自动写入insert的生成的key#>
    {
	    std::string sql = std::format("insert into `<#=tab.TabName#>` ({}) values({});", f.substr(0, f.length() - 1), values.substr(0, values.length() - 1));
        int query = mysql_query(connect, sql.c_str());
        // if (!query) return false;
    }
    {
        std::string sql = "SELECT LAST_INSERT_ID() as id;";
        int query = mysql_query(connect, sql.c_str());
        // if (!query) return false;
    }
	
    auto res = mysql_use_result(connect);
    if(res == nullptr) return false;

    MYSQL_ROW row;
    while ((row = mysql_fetch_row(res)) != nullptr)
    {
        v.<#=tab.Keys[0].Name#> = Columns::GetInt(row, 0);
        break;
    }
    mysql_free_result(res);
<#+}else{#>
	std::string sql = std::format("insert into `<#=tab.TabName#>` ({}) values({});", f.substr(0, f.length() - 1), values.substr(0, values.length() - 1));
	int query = mysql_query(connect, sql.c_str());
	if (!query) return false;
<#+}#>
	return true;
}

（c++代码多年没写，有可能有误，只是为了测试T4）

Roslyn+T4+EnvDTE ，基本上可以从一种数据源生成，另一种任意格式文本格式

视频演示

 代码

提取码：ynpb