/// <summary>
/// Initializes a new instance of the <see cref="UnionGraphType" /> class.
/// </summary>
/// <param name="name">The name.</param>
/// <param name="unionProxy">The proxy object which defined
/// the union type at design t.</param>
public UnionGraphType(string name, IGraphUnionProxy unionProxy)
{
this.Name = Validation.ThrowIfNullWhiteSpaceOrReturn(name, nameof(name));
this.Proxy = Validation.ThrowIfNullOrReturn(unionProxy, nameof(unionProxy));
_types = new HashSet <Type>();
_names = new List <string>();
this.Publish = true;
}
/// <summary>
/// Retrieves proxy instance defined on this attribute that is used to generate the <see cref="UnionGraphType" /> metadata.
/// </summary>
private void BuildUnionProxyInstance()
{
var fieldAttribute = this.SingleAttributeOfTypeOrDefault <GraphFieldAttribute>();
if (fieldAttribute == null)
{
return;
}
IGraphUnionProxy proxy = null;
if (fieldAttribute.Types.Count == 1)
{
var proxyType = fieldAttribute.Types.FirstOrDefault();
// declaring a proxy type overrides all other declarations for a union
// use it regardless of any names or other types that may be supplied
if (proxyType != null && Validation.IsCastable <IGraphUnionProxy>(proxyType))
{
var paramlessConstructor = proxyType.GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, Type.EmptyTypes, null);
if (paramlessConstructor == null)
{
throw new GraphTypeDeclarationException(
$"The union proxy type '{proxyType.FriendlyName()}' could not be instantiated. " +
"All union proxies must declare a parameterless constructor.");
}
proxy = InstanceFactory.CreateInstance(proxyType) as IGraphUnionProxy;
}
}
// when no proxy type is declared attempt to construct the proxy from types supplied
// if and only if a name was supplied for the union
if (proxy == null && !string.IsNullOrWhiteSpace(fieldAttribute.UnionTypeName))
{
proxy = new GraphUnionProxy(fieldAttribute.UnionTypeName, fieldAttribute.Types);
}
this.UnionProxy = proxy;
}
/// <summary>
/// Creates a union graph type from the given proxy.
/// </summary>
/// <param name="proxy">The proxy to convert to a union.</param>
/// <param name="ownerKind">The typekind of the <see cref="IGraphType"/> that sponsors this union.</param>
/// <returns>IUnionGraphType.</returns>
public IUnionGraphType CreateGraphType(IGraphUnionProxy proxy, TypeKind ownerKind)
{
if (proxy == null)
{
return(null);
}
var formatter = _schema.Configuration.DeclarationOptions.GraphNamingFormatter;
var name = formatter.FormatGraphTypeName(proxy.Name);
var union = new UnionGraphType(name, proxy)
{
Description = proxy.Description,
Publish = proxy.Publish,
};
foreach (var type in proxy.Types)
{
union.AddPossibleGraphType(
formatter.FormatGraphTypeName(GraphTypeNames.ParseName(type, ownerKind)),
type);
}
return(union);
}