Django 无法显示M2M关系中的所有结果

目前，我有以下实体关系模型：

表关系

 ------------          -----------------           ------
| Objective | ------- | Objective_Task | ---------| Task |
 ------------          -----------------           ------

我试图显示下表中的结果

| id  |        Task        |   Task status |     Objective      |
----------------------------------------------------------------
|  1  |  Set up drivers    | In progress   | Set up my machine  |
|  2  |  Configure network | In progress   | Set up the network |
|  3  |  Test the network  | In progress   | Set up the network |

但我得到的结果是：

| id  |        Task        |   Task status |        Objective          |
-----------------------------------------------------------------------
|  1  |  Set up drivers    | In progress   | objective.Objective.None  |
|  2  |  Configure network | In progress   | objective.Objective.None  |
|  3  |  Test the network  | In progress   | objective.Objective.None  |

以下是此实体关系的my class模型设置：

目标模型

class Objective(models.Model):
    id               = models.AutoField(primary_key=True)
    objective        = models.CharField(null=False, max_length=60)
    initial_date     = models.DateField(default=timezone.now(), null=False)
    expiration_date  = models.DateField()

    class Meta:
        ordering = ['initial_date']
        db_table = 'goal_objective'

class Task(models.Model):
    ACTIVE = 'Active'
    FINALIZED = 'Finalized'

    STATUS = [(ACTIVE, ACTIVE), (FINALIZED, FINALIZED)]

    id           = models.AutoField(primary_key=True)
    objective    = models.ManyToManyField(Objective)
    task         = models.CharField(null=False, max_length=140)
    status       = models.CharField(max_length=24, choices=STATUS, default=ACTIVE)

    class Meta:
        db_table = 'task_table'

{% for task in task_list %}
<table>
    <tbody>
        <tr>
         <td>{{task.id}}</td>
         <td>{{task.task}}</td>
         <td>{{task.status}}</td>
         <td>{{task.objective}}</td>
        </tr>
   </tbody>
</table>

任务模型

class Objective(models.Model):
    id               = models.AutoField(primary_key=True)
    objective        = models.CharField(null=False, max_length=60)
    initial_date     = models.DateField(default=timezone.now(), null=False)
    expiration_date  = models.DateField()

    class Meta:
        ordering = ['initial_date']
        db_table = 'goal_objective'

class Task(models.Model):
    ACTIVE = 'Active'
    FINALIZED = 'Finalized'

    STATUS = [(ACTIVE, ACTIVE), (FINALIZED, FINALIZED)]

    id           = models.AutoField(primary_key=True)
    objective    = models.ManyToManyField(Objective)
    task         = models.CharField(null=False, max_length=140)
    status       = models.CharField(max_length=24, choices=STATUS, default=ACTIVE)

    class Meta:
        db_table = 'task_table'

{% for task in task_list %}
<table>
    <tbody>
        <tr>
         <td>{{task.id}}</td>
         <td>{{task.task}}</td>
         <td>{{task.status}}</td>
         <td>{{task.objective}}</td>
        </tr>
   </tbody>
</table>

这是我用来填充表的代码

objective_ids = []
qs_current_objectives = Objective.objects.filter(initial_date__gte=date(2020,1,1), expiration_date__lte=date(2020,12,31)).values('id').values_list('id')

for value in qs_current_objectives:
    objective_ids.append(value)    

form = {'task_list': Task.objects.filter(objective__in=objective_ids)}

retrieval.html

class Objective(models.Model):
    id               = models.AutoField(primary_key=True)
    objective        = models.CharField(null=False, max_length=60)
    initial_date     = models.DateField(default=timezone.now(), null=False)
    expiration_date  = models.DateField()

    class Meta:
        ordering = ['initial_date']
        db_table = 'goal_objective'

class Task(models.Model):
    ACTIVE = 'Active'
    FINALIZED = 'Finalized'

    STATUS = [(ACTIVE, ACTIVE), (FINALIZED, FINALIZED)]

    id           = models.AutoField(primary_key=True)
    objective    = models.ManyToManyField(Objective)
    task         = models.CharField(null=False, max_length=140)
    status       = models.CharField(max_length=24, choices=STATUS, default=ACTIVE)

    class Meta:
        db_table = 'task_table'

{% for task in task_list %}
<table>
    <tbody>
        <tr>
         <td>{{task.id}}</td>
         <td>{{task.task}}</td>
         <td>{{task.status}}</td>
         <td>{{task.objective}}</td>
        </tr>
   </tbody>
</table>

{%用于任务列表%中的任务}
{{task.id}
{{task.task}
{{task.status}
{{task.objective}

---

在我的模型中，我遗漏了哪些我无法达到目标名称的地方？

为了避免将来出现问题，您应该更改一些内容

class Objective(models.Model):
    initial_date = models.DateField(default=timezone.now, null=False)

请注意，您传入的是函数，而不是调用

default

函数的结果。如果您执行现有操作，则每次重新启动web服务器时，默认值都会更改。将函数传递到默认值将把日期设置为当前日期

class Task(models.Model):
    objectives    = models.ManyToManyField(Objective, related_name='tasks')

使用单词的复数形式命名关系可以使代码更容易理解。现在，当您访问

task.objectives

时，您知道这是一个集合<代码>任务。目标让人觉得应该只有一个

在您的视图中，您不需要指定只需要id。只要您传递的是Queryset的实例，Django就会知道这一点。它还将只进行一次查询来获取数据

current_objectives = Objective.objects.filter(
    initial_date__gte=date(2020,1,1),
    expiration_date__lte=date(2020,12,31)
)
tasks = Task.objects.filter(objectives__in=current_objectives).distinct()
form = {'task_list': tasks}

也可以在过滤器中遍历关系

tasks = Task.objects.filter(
    objectives__initial_date__gte=date(2020,1,1),
    objectives__expiration_date__lte=date(2020,12,31),
).distinct()
form = {'task_list': tasks}

那么您的模板应该如下所示：

{% for task in task_list %}
<table>
    <tbody>
        <tr>
         <td>{{task.id}}</td>
         <td>{{task.task}}</td>
         <td>{{task.status}}</td>
         <td>{{task.objectives.all}}</td>
        </tr>
   </tbody>
</table>
{% endfor %}

{%用于任务列表%中的任务}
{{task.id}
{{task.task}
{{task.status}
{{task.objectives.all}
{%endfor%}

---

task.objective

（或当前代码中的

task.objective

）只是对Manager实例的引用，而不是集合本身。您需要访问

.all

以获取实际数据。

您是否填写了任务和目标之间的关系？非常感谢您的宝贵反馈！让我在代码中得到这些更改。我将尝试在输入此代码后尽快回复。如果不使用

任务.目标。所有

我只想显示目标的实际名称，该怎么办？我找到了上一条评论的解决方案，我必须创建一个自定义模板标记：