Dynamic length table in Flask form

Question

I have a flask web app that renders a Jinja2 template displaying multiple fields in a form. The form represents two tables in my database with a one-to-many relationship between the tables.

Record Class

class Record(db.Base):
    __tablename__ = 'metadata_record_version'
    id = Column(Integer, primary_key=True)
    number = Column(Float, nullable=False)

Extra Property Class

class Extra(db.Base):
    __tablename__ = 'extra'
    id = Column(Integer, primary_key=True)
    record_id = Column(Integer, ForeignKey('metadata_record_version.id'), nullable=False)
    key = Column(String(256), nullable=False)
    value = Column(String, nullable=False)
    metadata_record_version = relationship("MetadataRecordVersion")

The form allows the user to dynamically add more rows to a table containing the rows of extra. The user acheives this by clicking the + and - buttons on the form that call the relevant javascript functions. This part of my code works well and currently looks like:

Template.html

<form>
<!-- Other Form attributes here -->
<table id="extra-table">
    <tr>
        <th class="col-md-4">Property</th>
        <th class="col-md-4">Value</th>
        <th class="col-md-4"></th>
    </tr>
    {% for extra in form.extras %}
    <tr>
        <td>{{ extra.key(class_="form-control") }}</td>
        <td>{{ extra.value(class_="form-control") }}</td>
        <td>
            <button type="button" class="btn btn-danger"
                    onclick="removeExtraRow(this)">
                Remove <i class="fas fa-minus"></i>
            </button>
        </td>
    </tr>
    {% endfor %}
    <button type="button" class="btn btn-info" onclick="addExtraRow()">
        Add Row <i class="fas fa-plus"></i>
    </button>
</table>
</form>

<script> tag in Template.html

// Function to add a row to the Extra Properties Table
function addExtraRow() {
    let table = document.getElementById("extra-table");
    let row = table.insertRow(-1);
    row.contentEditable = "true";
    row.insertCell(0);
    row.insertCell(1);
    let cell3 = row.insertCell(2);
    cell3.innerHTML = "
    <button type=\"button\" class=\"btn btn-danger\" onclick=\"removeExtraRow(this)\"> Remove <i class=\"fas fa-minus\"></i> </button>";
}

// Function to remove a row from the extra properties table
function removeExtraRow(x) {
    let i = x.parentNode.parentNode["rowIndex"];
    let table = document.getElementById("extra-table");
    table.deleteRow(i);
}

The issue im facing is correctly receiving back the form data and passing it in WTForms.

How do I model in WTForms the dynamic length table? Currently when a row is added to the table it doesn't correctly post it back to the view.

Current form.py

class ExtraForm(Form):
    key = StringField('Property')
    value = StringField('Value')

class Edit(FlaskForm):
    version_number = FloatField('Version Number')
extras = FieldList(FormField(ExtraForm)

Edit: Added progress with regards to one-to-many relationship by use of FieldList(FormField(ExtraForm)).

Michael Betterton Michael Betterton · Accepted Answer · 2019-07-02T06:17:22

I was able to solve this by adding rows to the table that mimic the same format as the WTForm generated content. Below is the function for adding a new extra row.

function addExtraRow() {
    let table = document.getElementById("extra-table");
    let length = table.rows.length + 1;
    let row = table.insertRow(-1);
    let keyCell = row.insertCell(0);
    let valCell = row.insertCell(1);
    let cell3 = row.insertCell(2);
    keyCell.innerHTML = "<span class=\"bmd-form-group is-filled\"><input class=\"form-control\" id=\"extras-" + length + "-key\" name=\"extras-" + length + "-key\" required=\"\" type=\"text\" value=\"\"></span>";
    valCell.innerHTML = "<span class=\"bmd-form-group is-filled\"><input class=\"form-control\" id=\"extras-" + length + "-value\" name=\"extras-" + length + "-value\" required=\"\" type=\"text\" value=\"\"></span>";
    cell3.innerHTML = "<button type=\"button\" class=\"btn btn-danger\" onclick=\"removeExtraRow(this)\"> Remove <i class=\"fas fa-minus\"></i> </button>";
}

The content for what to insert into the cell' InnerHTML property was extracted by looking at the page source.

Dynamic length table in Flask form

1 Answers