目錄
ModelForm initial and instance：... 6
ModelForm
結合了form和model，將model的field類型映射成form的field類型，複用了model的驗證，還實現了存儲數據庫的簡單方法，寫更簡潔的代碼；
django提供一個輔助類（class Meta），使之可從Model創建Form；
生成的Form類中將具有和指定的模型字段對應的表單字段，順序爲fields屬性中指定的順序；
Model field與Form field：
每個模型字段有一個對應的默認表單字段，如模型中的ManyToManyField對應表單中的ModelMultipleChoiceField，ForeignKey<-->ModelChoiceField；
例：
mysite/books/models.py
TITLE_CHOICE = (
('MR', 'Mr.'),
('MRS', 'Mrs'),
('MS', 'Ms.'),
)
class Author(models.Model):
name = models.CharField(max_length=100)
title = models.CharField(max_length=3, choice=TITLE_CHOICE)
birth_date = models.DateField(blank=True, null=True)
def __str__(self):
return self.name
class Book(models.Model):
name = models.CharField(max_length=100)
authors = models.ManyToManyField(Author)
mysite/books/forms.py
from django import forms
from django.forms import ModelForm
from .models import Author, Book
class AuthorForm(ModelForm):
class Meta:
model = Author
fields = ['name', 'title', 'birth_date'] #使用model的全部字段，用field = '__all__'，另exclude = ('birth_date')排除的字段列表，建議顯式的設置，否則有安全問題
class BookForm(ModelForm):
class Meta:
model = Book
fields = ['name', 'authors']
# from .models import TITLE_CHOICE
# class AuthorForm(forms.Form):
# name = forms.CharField(max_length=100)
# title = forms.CharField(max_length=3, widget=forms.Select(choices=TITLE_CHOICE))
# birth_date = forms.DateField(required=False)
#
# class BookFrom(forms.Form):
# name = forms.CharField(max_length=100)
# authors = forms.ModelMultipleChoiceField(queryset=Author.objects.all())
注：
模型字段blank=True，表單字段require=False；
模型字段verbose_name（首字段大寫the first character capitalized），表單字段label；
模型字段help_text，表單字段help_text；
模型字段choices，表單字段widget=forms.Select(choices=TITLE_CHOICE)，choices從模型中來，選項通常會包含空選項，且默認會選擇，如果字段是必選的，它會強制用戶選擇一個選項，如果模型字段的default且有一個顯示default值，將不會包含空選項（初始值即blank=False）；
ModelForm save()方法：
這個方法根據表單綁定的數據創建並保存數據庫對象；
save()接受關鍵字參數commit，book=save(commit=False)時：
1將返回一個還沒有保存到數據庫的對象，這種情況下，要調用模型實例的form.save()，
2在多對多關係時指定commit=False，django不會立即爲多對多有關係保存表單數據（只有實例在數據庫中存在時纔可保存實例的多對多關係），要手動調用save_m2m()來保存多對多的表單數據
save_m2m()僅在save(commit=False)時纔用到；
>>> from publish.models import Author,Book
>>> from publish.forms import AuthorForm,BookForm
>>> form = AuthorForm({'name':'jowin','title':'MR'})
>>> form.is_valid()
True
>>> form.is_bound
True
>>> form.save() #author=form.save()，後續用返回的對象
<Author: jowin>
>>> form = AuthorForm({'name':'mage','title':'MR'})
>>> form.is_valid()
True
>>> form.save() #author=form.save()
<Author: mage>
>>> authors = Author.objects.all()
>>> authors_id = [author.id for author in authors]
>>> form = BookForm({'name':'django book','authors':authors_id})
>>> form.is_valid()
True
>>> form.save() #book=form.save()
<Book: Book object>
>>> form = BookForm({'name':'py book','authors':authors_id})
>>> form.is_valid()
True
>>> form.save()
<Book: Book object>
>>> form = BookForm({'name':'js book','authors':authors_id})
>>> form
<BookForm bound=True, valid=Unknown, fields=(name;authors)>
>>> book = form.save(commit=False)
>>> book
<Book: Book object>
>>> book.name = 'react book'
>>> book.save()
>>> form.save_m2m()
>>> book.name
'react book'
ModelForm Meta：
mysite/publish/forms.py
class AuthorForm(ModelForm):
class Meta:
model = Author
fields = ['name', 'title', 'birth_date'] #fields = '__all__';exclude = ('birth_date')
labels = {'name': 'Writer'}
widgets = {'name': Textarea(attrs={'cols': 80, 'rows': 20})} #forms.Textarea()
help_texts = {'name': 'Some useful help text'}
error_messages = {'name': {'max_length': "This writer's name is too long."}}
ModelForm自定義驗證：
mysite/publish/forms.py
class AuthorForm(ModelForm):
class Meta:
model = Author
fields = ['name', 'title', 'birth_date'] #fields = '__all__';exclude = ('birth_date')
labels = {'name': 'Writer'}
widgets = {'name': Textarea(attrs={'cols': 80, 'rows': 20})}
help_texts = {'name': 'Some useful help text'}
error_messages = {'name': {'max_length': "This writer's name is too long."}}
def clean(self):
cleaned_data = super(AuthorForm, self).clean()
name = cleaned_data.get('name')
title = cleaned_data.get('title')
if len(name) < 40 and title == 'MR':
raise ValidationError('Field: {} and {} is error'.format(name, title))
def clean_name(self): #clean_<field-name>
name = self.cleaned_data['name']
if len(name) < 30:
raise ValidationError('length must more than 30')
return name
ModelForm initial and instance：
提供初始值；
mysite/publish/views.py #view中使用modelform
from django.shortcuts import render, get_object_or_404
from django.http import HttpResponse
from .forms import AuthorForm
from .models import Author
def index(request):
if request.method == 'POST':
form = AuthorForm(request.POST)
if form.is_valid():
publish = form.save()
return HttpResponse('ok')
else:
form = AuthorForm()
return render(request, 'publish/publish.html', {'form': form})
def update(request, publish_id):
author = get_object_or_404(Author, id=publish_id)
if request.method == 'POST':
form = AuthorForm(request.POST, instance=author) #更新時要加instance，否則認爲是新創建，也可form=AuthorForm(request.POST,initial={'name':'test'})
if form.is_valid():
author = form.save()
return HttpResponse('add succeed')
form = AuthorForm(instance=author) #initial={'name':'test'}
return render(request, 'publish/publish.html', {'form': form})
mysite/publish/models.py
from django.db import models
TITLE_CHOICE = (
('MR', 'Mr.'),
('MRS', 'Mrs'),
('MS', 'Ms.'),
)
class Author(models.Model):
name = models.CharField(max_length=100)
title = models.CharField(max_length=3, choices=TITLE_CHOICE)
birth_date = models.DateField(blank=True, null=True)
def __str__(self):
return self.name
class Book(models.Model):
name = models.CharField(max_length=100)
authors = models.ManyToManyField(Author)