Python-屬性描敘符協議ORM實現原理依據- __set__ __get__ __delete__

class CheckString:
    def __init__(self, variable_type):
        self.variable_type = variable_type

    def __set__(self, instance, value):
        print('__set__:', value)
        self.value = "error：類型錯誤"
        if self.variable_type == 'str':
            self.value = value if isinstance(value, str) else "error：類型錯誤"

    def __get__(self, instance, owner):
        print("__get__")
        return self.value
        pass

    def __delete__(self, instance):
        pass


class InfoModel:
    name = CheckString(variable_type='str')


if __name__ == '__main__':
    info = InfoModel()
    info.name = "北門吹雪"
    print(info.name)

經過另一個類來描敘類變量的屬性類型，這個是ORM實現的核心基礎

給屬性賦值會調用 __set__方法，訪問屬性則會調用 __get__方法，則能夠獲取字段的對象和其值，刪除字段時候則調用 __delete__方法

 

北門吹雪: https://www.cnblogs.com/2bjiujiu/