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OData Complex Types

In the event an Entity Type definition uses a complex type, then the complex type is first created as a Rust struct.

The naming convention for a complex type is the Schema namespace followed by a dot . then the complex type name to which the prefix CT_ has been added.

E.G. In the BusinessPartner entity type, the Address property is the complex type GWSAMPLE_BASIC.CT_Address.

<EntityType Name="BusinessPartner" sap:content-version="1">
  <Key>
    <PropertyRef Name="BusinessPartnerID"/>
  </Key>
  <Property Name="Address" Type="GWSAMPLE_BASIC.CT_Address" Nullable="false"/>

  <!-- SNIP -->

</EntityType>

This refers to the <ComplexType> definition:

<ComplexType Name="CT_Address">
  <Property Name="City"        Type="Edm.String" MaxLength="40" sap:label="City"        sap:semantics="city"/>
  <Property Name="PostalCode"  Type="Edm.String" MaxLength="10" sap:label="Postal Code" sap:semantics="zip"/>
  <Property Name="Street"      Type="Edm.String" MaxLength="60" sap:label="Street"      sap:semantics="street"/>
  <Property Name="Country"     Type="Edm.String" MaxLength="3"  sap:label="Country"     sap:semantics="country"/>
  <Property Name="Building"    Type="Edm.String" MaxLength="10" sap:label="Building"/>
  <Property Name="AddressType" Type="Edm.String" MaxLength="2"  sap:label="Address Type"/>
</ComplexType>

So the above XML complex type definition is transformed into the following Rust struct:

#[derive(Clone, Debug, Default)]
pub struct CtAddress {
    pub address_type: Option<String>,
    pub building: Option<String>,
    pub city: Option<String>,
    pub country: Option<String>,
    pub postal_code: Option<String>,
    pub street: Option<String>,
}

Then the <EntityType> for BusinessPartner is translated into the following Rust struct

pub struct BusinessPartner {
    pub address: CtAddress,
    pub business_partner_id: String,
    //SNIP
}

OData "Simple" Complex Types

The metadata for the GWSAMPLE_BASIC OData service also contains the following complex type:

<ComplexType Name="CT_String">
  <Property Name="String" Type="Edm.String" Nullable="false" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
</ComplexType>

This particular type turns out not to be complex at all because it contains a single field of type Edm.String. Since this is directly equivalent to a standard Rust String, it would be redundant to wrap a single Rust String inside a struct.

Therefore, these "simple" complex types are ignored, and the corresponding <EntityType> field is declared simply as the equivalent Rust type.