面向对象之封装带来的好处

最新推荐文章于 2024-01-12 22:05:53 发布

最新推荐文章于 2024-01-12 22:05:53 发布 · 173 阅读

本文探讨了如何通过封装来简化比较不同DataObj类型的函数，避免重复代码，并提出了使用内部比较函数的方法来统一处理不同数据类型之间的比较操作。通过实例展示了如何实现lt_函数，该函数能够自动调用相应的比较方法，极大地提高了代码的复用性和可维护性。

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DataObj支持int float double三种类型，现在要设计一个less than函数，比较两个DataObj，并将结果存入到result中。一种实现：

inline void lt_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { (this->*lt_call_table[index])(obj1, obj2, result); } inline int lt_int_int_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { int64_t int1,int2; obj1.get_int(int1); obj2.get_int(int2); return result.set_int(int1 < int2); } inline int lt_int_float_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { int64_t int1; float float2; obj1.get_int(int1); obj2.get_float(float2); return result.set_int(int1 < float2); } inline int lt_int_double_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { int64_t int1; double double2; obj1.get_int(int1); obj2.get_double(double2); return result.set_int(int1 < double2); } inline int lt_float_int_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { float float1; int64_t int2; obj2.get_float(float1); obj1.get_int(int2); return result.set_int(float1 < int2); } inline int lt_float_float_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { float float1; float float2; obj2.get_float(float1); obj1.get_float(float2); return result.set_int(float1 < int2); } inline int lt_float_double_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { float float1; double double2; obj2.get_float(float1); obj1.get_double(double2); return result.set_int(float1 < double2); } inline int lt_double_int_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { double double1; int64_t int2; obj1.get_double(double1); obj2.get_int(int2); return result.set_int(double1 < int2); } inline int lt_double_float_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { double double1; float float2; obj1.get_double(double1); obj2.get_float(float2); return result.set_int(double1 < float2); } inline int lt_double_double_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { double double1; double double2; obj1.get_double(double1); obj2.get_double(double2); return result.set_int(double1 < double2); }

还好只有三种类型，只写了3*3中组合，如果还有更多类型，那就累死了！如何改进这个过程？封装。

inline int lt_(const DataObj &obj1, const DataObj &obj2, DataObj &result) { int err = ERR_SUCCESS; bool val; if (obj1.can_compare(obj2)) { val = (obj1 < obj2); result.set_int((int64_t)val); } else { err = ERR_INVALID_ARGUMENT; } return err; }

只要DataObj内部实现比较函数即可。

bool DataDataj::operator < (const DataDataj &that_obj) const { bool result = false; int err = DATA_SUCCESS; _DatajValue this_value; _DatajValue that_value; DataDatajType type = get_type(); switch (type) { case DataIntType: err = get_int(this_value.int_val); if (DATA_SUCCESS == err) { err = that_obj.get_int(that_value.int_val); if (DATA_SUCCESS == err) { result = this_value.int_val < that_value.int_val; } } break; case DataVarcharType: err = get_varchar(this_value.varchar_val); if (DATA_SUCCESS == err) { err = that_obj.get_varchar(that_value.varchar_val); if (DATA_SUCCESS == err) { result = this_value.varchar_val < that_value.varchar_val; } } break; case DataFloatType: err = get_float(this_value.float_val); if (DATA_SUCCESS == err) { err = that_obj.get_float(that_value.float_val); if (DATA_SUCCESS == err) { result = this_value.float_val < that_value.float_val; } } break; case DataDoubleType: err = get_double(this_value.double_val); if (DATA_SUCCESS == err) { err = that_obj.get_double(that_value.double_val); if (DATA_SUCCESS == err) { result = this_value.double_val < that_value.double_val; } } break; } return result; }