flask-admin: How to make columns read-only according to other columns' value?

Question

I've built a system that allows users to apply for code review and wait for manager to approve.

And now what I want to achieve is as below:

1. If it's approved, then all the fields become read-only(I manually set Project name as read-only here):

2. If it's rejected,

   

   then all the fields become editable. Of course, when creating a new project, all the fields should be editable.
   

   The code of class Project and ProjectView are as below:

    from flask_sqlalchemy import SQLAlchemy
    from flask_admin.contrib import sqla
    from flask_security import current_user
   
    # Create Flask application
    app = Flask(__name__)
    app.config.from_pyfile('config.py')
    db = SQLAlchemy(app)
   
    class Project(db.Model):
   
           id = db.Column(db.Integer, primary_key=True)
           project_name = db.Column(db.Unicode(128))
           version = db.Column(db.Unicode(128))
           SVN = db.Column(db.UnicodeText)
           approve = db.Column(db.Boolean())
   
           def __unicode__(self):
               return self.name
   
    class ProjectView(sqla.ModelView):
        def is_accessible(self):
            if not current_user.is_active or not current_user.is_authenticated:
                return False
            return False
   
        @property
        def _form_edit_rules(self):
            return rules.RuleSet(self, self.form_rules)
   
        @_form_edit_rules.setter
        def _form_edit_rules(self, value):
            pass
   
        @property
        def _form_create_rules(self):
            return rules.RuleSet(self, self.form_rules)
   
        @_form_create_rules.setter
        def _form_create_rules(self, value):
            pass
   
        @property
        def form_rules(self):
        form_rules = [
            rules.Field('project_name'),
            rules.Field('version'),
            rules.Field('SVN'),
        ]
        if not has_app_context() or current_user.has_role('superuser'):
            form_rules.append('approve')
   

   In my opinion, since approve is a boolean variable, there should be a condition judgement to tell if it is 0 or 1 and then the field become read-only or editable accordingly.

   Thanks for any advise in advance.

Answer 1

As you already noticed setting readonly property for a field is rather simple but making it dynamic is a bit tricky.

First of all you need a custom field class:

from wtforms.fields import StringField

class ReadOnlyStringField(StringField):
    @staticmethod
    def readonly_condition():
        # Dummy readonly condition
        return False

    def __call__(self, *args, **kwargs):
        # Adding `readonly` property to `input` field
        if self.readonly_condition():
            kwargs.setdefault('readonly', True)
        return super(ReadOnlyStringField, self).__call__(*args, **kwargs)

    def populate_obj(self, obj, name):
        # Preventing application from updating field value
        # (user can modify web page and update the field)
        if not self.readonly_condition():
            super(ReadOnlyStringField, self).populate_obj(obj, name)

Set form_overrides attribute for your view:

class ProjectView(sqla.ModelView):
    form_overrides = {
        'project_name': ReadOnlyStringField
    }

You need to pass custom readonly_condition function to ReadOnlyStringField instance. The easiest way I found is overriding edit_form method:

class ProjectView(sqla.ModelView):
    def edit_form(self, obj=None):
        def readonly_condition():
            if obj is None:
                return False
            return obj.approve
        form = super(ProjectView, self).edit_form(obj)
        form.project_name.readonly_condition = readonly_condition
        return form

Happy coding!

Answer 2

The previous answer I put on here had a major flaw. The following uses a different approach by analyzing the form itself and adding readonly: True to render_kw for a particular form if a certain condition is met.

class ProjectView(sqla.ModelView):
    # ... other class code

    def edit_form(self, obj=None):
        # grab form from super
        form = super(ProjectView, self).edit_form(obj)

        # form.approved.data should be the same as approved
        # if approved is included in the form
        if form.approved.data:
            if form.project_name.render_kw:
                form.project_name.render_kw.update({
                    'readonly': True
                })
            else:
                form.project_name.render_kw = {'readonly': True}
        return form

This is a bit hacky, and it requires that approved be in the edit form. If you used this solution, you could either add approved as a readonly field or, instead of readonly, you could remove the approved field from the form in the above class method.

Answer 3

For me this trick was the simplest way to do it:

from flask_sqlalchemy import SQLAlchemy
from flask_admin.contrib.sqla import ModelView
from flask_admin.form.rules import Field


class Example(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    not_editable = db.Column(db.Unicode(128))
    editable = db.Column(db.Unicode(128))


class ReadonlyFiledRule(Field):
    def __call__(self, form, form_opts=None, field_args={}):
        field_args['readonly'] = True
        return super(ReadonlyFiledRule, self).__call__(form, form_opts, field_args)


class ExampleView(ModelView):
    form_edit_rules = (ReadonlyFiledRule('not_editable'), 'editable', )

Update (the easiest way):

class ExampleView(ModelView):
    form_widget_args = {
        'not_editable': {
            'readonly': True
        }
    }