protected virtual Syntax Validate()
{
Required.Select(acceptor => TokenOf(acceptor)).Count();
return(this);
}
/// <summary>
/// Creates an instance of the specified type, using any available services.
/// The strategy is to use the longest public constructor.
/// </summary>
/// <param name="monitor">Monitor to use.</param>
/// <param name="t">Type of the object to create.</param>
/// <param name="services">Available services to inject.</param>
/// <param name="requiredParameters">Optional required parameters.</param>
/// <returns>The object instance or null on error.</returns>
public static object?Create(IActivityMonitor monitor, Type t, IServiceProvider services, IEnumerable <object>?requiredParameters = null)
{
Throw.CheckNotNullArgument(monitor);
Throw.CheckNotNullArgument(t);
using (monitor.OpenDebug($"Creating instance of type: {t.AssemblyQualifiedName}."))
try
{
Required required = requiredParameters == null
? Array.Empty <KeyValuePair <object?, Type> >()
: (Required)requiredParameters.Select(r => new KeyValuePair <object?, Type>(r, r.GetType())).ToList();
var longestCtor = t.GetConstructors()
.Select(x => ValueTuple.Create(x, x.GetParameters()))
.Where(x => x.Item2.Length >= required.Count)
.OrderByDescending(x => x.Item2.Length)
.Select(x => new
{
Ctor = x.Item1,
Parameters = x.Item2,
Mapped = x.Item2
.Select(p => required.FirstOrDefault(r => p.ParameterType.IsAssignableFrom(r.Value)).Key)
.ToArray()
})
.Where(x => x.Mapped.Count(m => m != null) == required.Count)
.FirstOrDefault();
if (longestCtor == null)
{
var msg = $"Unable to find a public constructor for '{t.FullName}'.";
if (required.Count > 0)
{
msg += " With required parameters compatible with type: " + required.Select(r => r.Value.Name).Concatenate();
}
monitor.Error(msg);
return(null);
}
int failCount = 0;
for (int i = 0; i < longestCtor.Mapped.Length; ++i)
{
if (longestCtor.Mapped[i] == null)
{
var p = longestCtor.Parameters[i];
var resolved = services.GetService(p.ParameterType);
if (resolved == null && !p.HasDefaultValue)
{
monitor.Error($"Resolution failed for parameter '{p.Name}', type: '{p.ParameterType}'.");
++failCount;
}
longestCtor.Mapped[i] = resolved;
}
}
if (failCount > 0)
{
monitor.Error($"Unable to resolve parameters for '{t.FullName}'. Considered longest constructor: {longestCtor.Ctor}.");
return(null);
}
return(longestCtor.Ctor.Invoke(longestCtor.Mapped));
}
catch (Exception ex)
{
monitor.Error($"While instantiating {t.FullName}.", ex);
return(null);
}
}
public bool IsRequired(PropertyInfo pi)
{
return(Required.Select(p => p.ToLower()).Contains(pi.Name.ToLower()));
}