tableau · t8y8 · Feb 16, 2017 · Nov 6, 2016 · Jan 29, 2017 · Jan 29, 2017
diff --git a/tableaudocumentapi/datasource.py b/tableaudocumentapi/datasource.py
@@ -240,9 +240,12 @@ def clear_repository_location(self):
     @property
     def fields(self):
         if not self._fields:
-            self._fields = self._get_all_fields()
+            self._refresh_fields()
         return self._fields
 
+    def _refresh_fields(self):
+        self._fields = self._get_all_fields()
+
     def _get_all_fields(self):
         column_field_objects = self._get_column_objects()
         existing_column_fields = [x.id for x in column_field_objects]
@@ -258,3 +261,77 @@ def _get_metadata_objects(self):
     def _get_column_objects(self):
         return [_column_object_from_column_xml(self._datasourceTree, xml)
                 for xml in self._datasourceTree.findall('.//column')]
+
+    def add_field(self, name, datatype, role, field_type, caption):
+        """ Adds a base field object with the given values.
+
+        Args:
+            name: Name of the new Field. String.
+            datatype:  Datatype of the new field. String.
+            role:  Role of the new field. String.
+            field_type:  Type of the new field. String.
+            caption:  Caption of the new field. String.
+
+        Returns:
+            The new field that was created. Field.
+        """
+        # TODO: A better approach would be to create an empty column and then
+        # use the input validation from its "Field"-object-representation to set values.
+        # However, creating an empty column causes errors :(
+
+        # If no caption is specified, create one with the same format Tableau does
+        if not caption:
+            caption = name.replace('[', '').replace(']', '').title()
+
+        # Create the elements
+        column = Field.create_field_xml(caption, datatype, role, field_type, name)
+
+        self._datasourceTree.getroot().append(column)
+
+        # Refresh fields to reflect changes and return the Field object
+        self._refresh_fields()
+        return self.fields[name]
+
+    def remove_field(self, field):
+        """ Remove a given field
+
+        Args:
+            field: The field to remove. ET.Element
+
+        Returns:
+            None
+        """
+        if not field or not isinstance(field, Field):
+            raise ValueError("Need to supply a field to remove element")
+
+        self._datasourceTree.getroot().remove(field.xml)
+        self._refresh_fields()
+
+    ###########
+    # Calculations
+    ###########
+    @property
+    def calculations(self):
+        """ Returns all calculated fields.
+        """
+        return {k: v for k, v in self.fields.items() if v.calculation is not None}
+
+    def add_calculation(self, caption, formula, datatype, role, type):
+        """ Adds a calculated field with the given values.
+
+        Args:
+            caption:  Caption of the new calculation. String.
+            formula:  Formula of the new calculation. String.
+            datatype:  Datatype of the new calculation. String.
+            role:  Role of the new calculation. String.
+            type:  Type of the new calculation. String.
+
+        Returns:
+            The new calculated field that was created. Field.
+        """
+        # Dynamically create the name of the field
+        name = '[Calculation_{}]'.format(str(uuid4().int)[:18])
+        field = self.add_field(name, datatype, role, type, caption)
+        field.calculation = formula
+
+        return field
diff --git a/tableaudocumentapi/field.py b/tableaudocumentapi/field.py
@@ -1,6 +1,7 @@
 import functools
 import xml.etree.ElementTree as ET
 
+from tableaudocumentapi.property_decorators import argument_is_one_of
 
 _ATTRIBUTES = [
     'id',           # Name of the field as specified in the file, usually surrounded by [ ]
@@ -45,12 +46,14 @@ def __init__(self, column_xml=None, metadata_xml=None):
 
         if column_xml is not None:
             self._initialize_from_column_xml(column_xml)
+            self._xml = column_xml
             # This isn't currently never called because of the way we get the data from the xml,
             # but during the refactor, we might need it.  This is commented out as a reminder
             # if metadata_xml is not None:
             #     self.apply_metadata(metadata_xml)
 
         elif metadata_xml is not None:
+            self._xml = metadata_xml
             self._initialize_from_metadata_xml(metadata_xml)
 
         else:
@@ -66,6 +69,16 @@ def _initialize_from_metadata_xml(self, xmldata):
                                   read_name=metadata_name)
         self.apply_metadata(xmldata)
 
+    @classmethod
+    def create_field_xml(cls, caption, datatype, role, field_type, name):
+        column = ET.Element('column')
+        column.set('caption', caption)
+        column.set('datatype', datatype)
+        column.set('role', role)
+        column.set('type', field_type)
+        column.set('name', name)
+        return column
+
     ########################################
     # Special Case methods for construction fields from various sources
     # not intended for client use
@@ -116,52 +129,200 @@ def id(self):
         """ Name of the field as specified in the file, usually surrounded by [ ] """
         return self._id
 
+    @property
+    def xml(self):
+        """ XML representation of the field. """
+        return self._xml
+
+    ########################################
+    # Attribute getters and setters
+    ########################################
+
     @property
     def caption(self):
         """ Name of the field as displayed in Tableau unless an aliases is defined """
         return self._caption
 
+    @caption.setter
+    def caption(self, caption):
+        """ Set the caption of a field
+
+            Args:
+                caption:  New caption. String.
+
+            Returns:
+                Nothing.
+        """
+        self._caption = caption
+        self._xml.set('caption', caption)
+
     @property
     def alias(self):
         """ Name of the field as displayed in Tableau if the default name isn't wanted """
         return self._alias
 
+    @alias.setter
+    def alias(self, alias):
+        """ Set the alias of a field
+
+            Args:
+                alias:  New alias. String.
+
+            Returns:
+                Nothing.
+        """
+        self._alias = alias
+        self._xml.set('alias', alias)
+
     @property
     def datatype(self):
         """ Type of the field within Tableau (string, integer, etc) """
         return self._datatype
 
+    @datatype.setter
+    @argument_is_one_of('string', 'integer', 'date', 'boolean')
+    def datatype(self, datatype):
+        """ Set the datatype of a field
+
+            Args:
+                datatype:  New datatype. String.
+
+            Returns:
+                Nothing.
+        """
+        self._datatype = datatype
+        self._xml.set('datatype', datatype)

     @property
     def role(self):
         """ Dimension or Measure """
         return self._role
 
+    @role.setter
+    @argument_is_one_of('dimension', 'measure')
+    def role(self, role):
+        """ Set the role of a field
+
+            Args:
+                role:  New role. String.
+
+            Returns:
+                Nothing.
+        """
+        self._role = role
+        self._xml.set('role', role)
+
+    @property
+    def type(self):
+        """ Dimension or Measure """
+        return self._type
+
+    @type.setter
+    @argument_is_one_of('quantitative', 'ordinal', 'nominal')
+    def type(self, field_type):
+        """ Set the type of a field
+
+            Args:
+                field_type:  New type. String.
+
+            Returns:
+                Nothing.
+        """
+        self._type = field_type
+        self._xml.set('type', field_type)
+
+    ########################################
+    # Aliases getter and setter
+    # Those are NOT the 'alias' field of the column,
+    # but instead the key-value aliases in its child elements
+    ########################################
+
+    def add_alias(self, key, value):
+        """ Add an alias for a given display value.
+
+            Args:
+                key:  The data value to map. Example: "1". String.
+                value: The display value for the key. Example: "True". String.
+            Returns:
+                Nothing.
+        """
+
+        # determine whether there already is an aliases-tag
+        aliases = self._xml.find('aliases')
+        # and create it if there isn't
+        if not aliases:
+            aliases = ET.Element('aliases')
+            self._xml.append(aliases)
+
+        # find out if an alias with this key already exists and use it
+        existing_alias = [tag for tag in aliases.findall('alias') if tag.get('key') == key]
+        # if not, create a new ET.Element
+        alias = existing_alias[0] if existing_alias else ET.Element('alias')
+
+        alias.set('key', key)
+        alias.set('value', value)
+        if not existing_alias:
+            aliases.append(alias)
+
+    @property
+    def aliases(self):
+        """ Returns all aliases that are registered under this field.
+
+        Returns:
+            Key-value mappings of all registered aliases. Dict.
+        """
+        aliases_tag = self._xml.find('aliases') or []
+        return {a.get('key', 'None'): a.get('value', 'None') for a in list(aliases_tag)}
+
+    ########################################
+    # Attribute getters
+    ########################################
+
     @property
     def is_quantitative(self):
         """ A dependent value, usually a measure of something
 
         e.g. Profit, Gross Sales """
-        return self._type == 'quantitative'
+        return self.type == 'quantitative'
 
     @property
     def is_ordinal(self):
         """ Is this field a categorical field that has a specific order
 
         e.g. How do you feel? 1 - awful, 2 - ok, 3 - fantastic """
-        return self._type == 'ordinal'
+        return self.type == 'ordinal'
 
     @property
     def is_nominal(self):
         """ Is this field a categorical field that does not have a specific order
 
         e.g. What color is your hair? """
-        return self._type == 'nominal'
+        return self.type == 'nominal'
 
     @property
     def calculation(self):
         """ If this field is a calculated field, this will be the formula """
         return self._calculation
 
+    @calculation.setter
+    def calculation(self, new_calculation):
+        """ Set the calculation of a calculated field.
+
+        Args:
+            new_calculation: The new calculation/formula of the field. String.
+        """
+        if self.calculation is None:
+            calculation = ET.Element('calculation')
+            calculation.set('class', 'tableau')
+            calculation.set('formula', new_calculation)
+            # Append the elements to the respective structure
+            self._xml.append(calculation)
+
+        else:
+            self._xml.find('calculation').set('formula', new_calculation)
+
+        self._calculation = new_calculation
+
     @property
     def default_aggregation(self):
         """ The default type of aggregation on the field (e.g Sum, Avg)"""

diff --git a/tableaudocumentapi/property_decorators.py b/tableaudocumentapi/property_decorators.py
@@ -0,0 +1,16 @@
+from functools import wraps
+
+
+def argument_is_one_of(*allowed_values):
+    def property_type_decorator(func):
+        @wraps(func)
+        def wrapper(self, value):
+            if value not in allowed_values:
+                error = "Invalid argument: {0}. {1} must be one of {2}."
+                msg = error.format(value, func.__name__, allowed_values)
+                raise ValueError(error)
+            return func(self, value)
+
+        return wrapper
+
+    return property_type_decorator
diff --git a/test/assets/.gitignore b/test/assets/.gitignore
@@ -0,0 +1 @@
+field_change_test_output.tds