创建一个简单的orm 基类

import json

from utils import log


def save(data, path):
    """
    data 是 dict 或者 list
    path 是保存文件的路径
    """
    s = json.dumps(data, indent=2, ensure_ascii=False)
    with open(path, 'w+', encoding='utf-8') as f:
        # log('save', path, s, data)
        f.write(s)
        

# 读取文件信息
def load(path):
    with open(path, 'r', encoding='utf-8') as f:
        s = f.read()
        # log('load', s)
        return json.loads(s)

class Model:
    """
    数据存储的基类
    """
    
    # 获取储存地址
    @classmethod
    def db_path(cls):
        """
        那个类使用，获取那个类的类名，和保存文件一直 
        """
        classname = cls.__name__
        path = 'data/{}.txt'.format(classname)
        return path
    
    @classmethod
    def all(cls):
        path = cls.db_path()
        # 读取文件将字符串转换成python 对象
        models = load(path)
        # 参考django orm  all方法
        ms = [cls(m) for m in models]
        return ms
    
    @classmethod
    def find_all(cls, **kwargs):
        """
        类似 django fittler().all()
        :param kwargs: 
        :return: 
        """
        ms = []
        log('kwargs, ', kwargs, type(kwargs))
        k, v ='',''
        for key, value in kwargs.items():
            k, v =key, value
        all = cls.all()
        # 得到所有的 对象
        for m in all:
            # 利用dict的魔方方法获取对应的k,v ,判断查询的对象是否存在
            if v == m.__dict__[k]:
                ms.append(m)
        return ms

    @classmethod
    def find_by(cls, **kwargs):
        """
        用法如下，kwargs 是只有一个元素的 dict
        u = User.find_by(username='gua')
        类似djangofirst 返回第一个值
        """
        log('kwargs, ', kwargs, type(kwargs))
        k, v = '', ''
        for key, value in kwargs.items():
            k, v = key, value
        all = cls.all()
        for m in all:
            # 也可以用 getattr(m, k) 取值
            if v == m.__dict__[k]:
                return m
        return None

    @classmethod
    def find(cls, id):
        """
        只查询 id
        :param id: 
        :return: 
        """
        return cls.find_by(id=id)
    
    @classmethod
    def delete(cls, id):
        """
        删除 先找到全部，然后删除指定
        """
        models = cls.all()
        index = -1
        for i,e in enumerate(models):
            if e.id == id:
                index = i
                break
        if index == -1:
            # 没找到
            pass
        else:
            models.pop(index)
            # 根据init 来保存记录文件
            l = [m.__dict__ for m in models]
            path = cls.db_path()
            save(l, path)
            return

    def __repr__(self):
        """
        __repr__ 是一个魔法方法
        简单来说, 它的作用是得到类的 字符串表达 形式
        比如 print(u) 实际上是 print(u.__repr__())
        """
        classname = self.__class__.__name__
        properties = ['{}: ({})'.format(k, v) for k, v in self.__dict__.items()]
        s = '\n'.join(properties)
        return '< {}\n{} \n>\n'.format(classname, s)
    
    def save(self):
        """
        先读取所有内容，在吧要添加的内容添加进去
        :return: 
        """
        models = self.all()
        if self.id is None:
            # 设置 self.id
            # 先看看是否是空 list
            if len(models) == 0:
                # 我们让第一个元素的 id 为 1（当然也可以为 0）
                self.id = 1
            else:
                m = models[-1]
                # log('m', m)
                self.id = m.id + 1
            models.append(self)
        else:
            # 更改内容
            # index = self.find(self.id)
            index = -1
            for i, m in enumerate(models):
                if m.id == self.id:
                    index = i
                    break
            log('debug', index)
            models[index] = self
        l = [m.__dict__ for m in models]
        path = self.db_path()
        save(l, path)