[Foundation] Add helper methods to NSArray to create managed arrays of strongly typed dictionaries.

src/AudioToolbox/AudioToolbox.cs

@@ -129,21 +129,14 @@ public static class SoundBank {
 			if (url is null)
 				ObjCRuntime.ThrowHelper.ThrowArgumentNullException (nameof (url));
 
-			InstrumentInfo []? result = null;
 			IntPtr array = IntPtr.Zero;
-			OSStatus error;
 			unsafe {
-				error = CopyInstrumentInfoFromSoundBank (url.Handle, &array);
+				var error = CopyInstrumentInfoFromSoundBank (url.Handle, &array);
 				GC.KeepAlive (url);
+				if (error != 0)
+					return null;
 			}
-			if (array != IntPtr.Zero) {
-				var dicts = NSArray.ArrayFromHandle<NSDictionary> (array);
-				result = new InstrumentInfo [dicts.Length];
-				for (int i = 0; i < dicts.Length; i++)
-					result [i] = new InstrumentInfo (dicts [i]);
-				CFObject.CFRelease (array);
-			}
-			return (error != 0) ? null : result;
+			return NSArray.DictionaryArrayFromHandleDropNullElements<InstrumentInfo> (array, dict => new InstrumentInfo (dict), releaseHandle: true);
 		}
 	}
 }

src/AudioUnit/AudioComponent.cs

@@ -671,7 +671,7 @@ public AudioComponentInfo []? ComponentList {
 			get {
 				using var nameHandle = new TransientCFString (Name);
 				var cHandle = AudioUnitExtensionCopyComponentList (nameHandle);
-				return NSArray.ArrayFromHandle<AudioComponentInfo> (cHandle, h => new AudioComponentInfo (Runtime.GetNSObject<NSDictionary> (h)!), releaseHandle: true);
+				return NSArray.DictionaryArrayFromHandleDropNullElements<AudioComponentInfo> (cHandle, h => new AudioComponentInfo (h), releaseHandle: true);
 			}
 			set {
 				using var nameHandle = new TransientCFString (Name);

src/CoreFoundation/CFProxySupport.cs

@@ -263,7 +263,7 @@ public static partial class CFNetwork {
 			/* CFStringRef __nonnull */ IntPtr proxyAutoConfigurationScript,
 			/* CFURLRef __nonnull */ IntPtr targetURL, /* CFErrorRef  __nullable * __nullable */ IntPtr* error);
 
-		static NSArray? CopyProxiesForAutoConfigurationScript (NSString proxyAutoConfigurationScript, NSUrl targetURL)
+		static IntPtr CopyProxiesForAutoConfigurationScript (NSString proxyAutoConfigurationScript, NSUrl targetURL)
 		{
 			IntPtr err;
 			IntPtr native;
@@ -272,7 +272,7 @@ public static partial class CFNetwork {
 				GC.KeepAlive (proxyAutoConfigurationScript);
 				GC.KeepAlive (targetURL);
 			}
-			return native == IntPtr.Zero ? null : new NSArray (native);
+			return native;
 		}
 
 		/// <param name="proxyAutoConfigurationScript">JavaScript source to be executed to obtain a list of proxies to use.</param>
@@ -288,21 +288,9 @@ public static partial class CFNetwork {
 			if (targetURL is null)
 				ObjCRuntime.ThrowHelper.ThrowArgumentNullException (nameof (targetURL));
 
-			using (var array = CopyProxiesForAutoConfigurationScript (proxyAutoConfigurationScript, targetURL)) {
-				if (array is null)
-					return null;
-
-				NSDictionary [] dictionaries = NSArray.ArrayFromHandle<NSDictionary> (array.Handle);
-				GC.KeepAlive (array);
-				if (dictionaries is null)
-					return null;
-
-				CFProxy [] proxies = new CFProxy [dictionaries.Length];
-				for (int i = 0; i < dictionaries.Length; i++)
-					proxies [i] = new CFProxy (dictionaries [i]);
-
-				return proxies;
-			}
+			var array = CopyProxiesForAutoConfigurationScript (proxyAutoConfigurationScript, targetURL);
+			var proxies = NSArray.DictionaryArrayFromHandleDropNullElements (array, (dict) => new CFProxy (dict), releaseHandle: true);
+			return proxies;
 		}
 
 		/// <include file="../../docs/api/CoreFoundation/CFNetwork.xml" path="/Documentation/Docs[@DocId='M:CoreFoundation.CFNetwork.GetProxiesForAutoConfigurationScript(Foundation.NSString,System.Uri)']/*" />
@@ -325,12 +313,12 @@ public static partial class CFNetwork {
 			/* CFURLRef __nonnull */ IntPtr url,
 			/* CFDictionaryRef __nonnull */ IntPtr proxySettings);
 
-		static NSArray? CopyProxiesForURL (NSUrl url, NSDictionary proxySettings)
+		static IntPtr CopyProxiesForURL (NSUrl url, NSDictionary proxySettings)
 		{
 			IntPtr native = CFNetworkCopyProxiesForURL (url.Handle, proxySettings.Handle);
 			GC.KeepAlive (url);
 			GC.KeepAlive (proxySettings);
-			return native == IntPtr.Zero ? null : new NSArray (native);
+			return native;
 		}
 
 		/// <param name="url">The target URL to connect to.</param>
@@ -349,21 +337,9 @@ public static partial class CFNetwork {
 			if (proxySettings is null)
 				return null;
 
-			using (NSArray? array = CopyProxiesForURL (url, proxySettings.Dictionary)) {
-				if (array is null)
-					return null;
-
-				NSDictionary [] dictionaries = NSArray.ArrayFromHandle<NSDictionary> (array.Handle);
-				GC.KeepAlive (array);
-				if (dictionaries is null)
-					return null;
-
-				CFProxy [] proxies = new CFProxy [dictionaries.Length];
-				for (int i = 0; i < dictionaries.Length; i++)
-					proxies [i] = new CFProxy (dictionaries [i]);
-
-				return proxies;
-			}
+			var array = CopyProxiesForURL (url, proxySettings.Dictionary);
+			var proxies = NSArray.DictionaryArrayFromHandleDropNullElements (array, (dict) => new CFProxy (dict), releaseHandle: true);
+			return proxies;
 		}
 
 		/// <param name="uri">The target Uri to connect to.</param>

src/CoreText/CTFont.cs

@@ -3475,10 +3475,7 @@ public nint GetLigatureCaretPositions (CGGlyph glyph, nfloat [] positions)
 		public CTFontVariationAxes [] GetVariationAxes ()
 		{
 			var cfArrayRef = CTFontCopyVariationAxes (Handle);
-			if (cfArrayRef == IntPtr.Zero)
-				return Array.Empty<CTFontVariationAxes> ();
-			return NSArray.ArrayFromHandle (cfArrayRef,
-					d => new CTFontVariationAxes (Runtime.GetNSObject<NSDictionary> (d)!), true);
+			return NSArray.NonNullDictionaryArrayFromHandleDropNullElements (cfArrayRef, d => new CTFontVariationAxes (d), true);
 		}
 
 		[DllImport (Constants.CoreTextLibrary)]
@@ -3507,10 +3504,8 @@ public CTFontVariationAxes [] GetVariationAxes ()
 		public CTFontFeatures [] GetFeatures ()
 		{
 			var cfArrayRef = CTFontCopyFeatures (Handle);
-			if (cfArrayRef == IntPtr.Zero)
-				return Array.Empty<CTFontFeatures> ();
-			return NSArray.ArrayFromHandle (cfArrayRef,
-					d => new CTFontFeatures (Runtime.GetNSObject<NSDictionary> (d)!), true);
+			return NSArray.NonNullDictionaryArrayFromHandleDropNullElements (cfArrayRef,
+					d => new CTFontFeatures (d), true);
 		}
 
 		[DllImport (Constants.CoreTextLibrary)]
@@ -3523,10 +3518,8 @@ public CTFontFeatures [] GetFeatures ()
 		public CTFontFeatureSettings [] GetFeatureSettings ()
 		{
 			var cfArrayRef = CTFontCopyFeatureSettings (Handle);
-			if (cfArrayRef == IntPtr.Zero)
-				return Array.Empty<CTFontFeatureSettings> ();
-			return NSArray.ArrayFromHandle (cfArrayRef,
-					d => new CTFontFeatureSettings (Runtime.GetNSObject<NSDictionary> (d)!), true);
+			return NSArray.NonNullDictionaryArrayFromHandleDropNullElements (cfArrayRef,
+					d => new CTFontFeatureSettings (d), true);
 		}
 		#endregion
 

src/Foundation/NSArray.cs

@@ -623,6 +623,64 @@ public static T [] ArrayFromHandleFunc<T> (NativeHandle handle, Func<NativeHandl
 			return rv;
 		}
 
+		/// <summary>Creates a managed array from a pointer to a native NSArray of NSDictionary objects, dropping null and NSNull elements.</summary>
+		/// <typeparam name="T">The type of objects to create from the dictionaries.</typeparam>
+		/// <param name="handle">The pointer to the native NSArray instance containing NSDictionary objects.</param>
+		/// <param name="createObjectFromDictionary">A factory function that creates an instance of type T from an NSDictionary.</param>
+		/// <param name="releaseHandle">Whether the native NSArray instance should be released before returning or not. Defaults to false.</param>
+		/// <returns>A C# array with the values, or null if the handle is zero. Null and NSNull elements are excluded from the result.</returns>
+		/// <remarks>
+		///   <para>This method converts a native NSArray of NSDictionary objects into a managed array. Any null or NSNull elements in the source array are skipped, and the resulting array is resized accordingly.</para>
+		/// </remarks>
+#nullable enable
+		internal static T []? DictionaryArrayFromHandleDropNullElements<T> (NativeHandle handle, Func<NSDictionary, T> createObjectFromDictionary, bool releaseHandle = false)
+		{
+			if (handle == NativeHandle.Zero)
+				return null;
+
+			try {
+				var count = GetCount (handle);
+				var ret = new T [count];
+				nuint nextIndex = 0;
+
+				for (nuint i = 0; i < count; i++) {
+					var val = GetAtIndex (handle, i);
+					if (val == IntPtr.Zero || val == NSNull.Null.Handle)
+						continue;
+					var dict = Runtime.GetNSObject<NSDictionary> (val);
+					if (dict is null)
+						continue;
+					ret [nextIndex++] = createObjectFromDictionary (dict);
+				}
+
+				if (nextIndex != count)
+					Array.Resize<T> (ref ret, (int) nextIndex);
+
+				return ret;
+			} finally {
+				if (releaseHandle)
+					NSObject.DangerousRelease (handle);
+			}
+		}
+
+		/// <summary>Creates a managed array from a pointer to a native NSArray of NSDictionary objects, dropping null and NSNull elements. Always returns a non-null array.</summary>
+		/// <typeparam name="T">The type of objects to create from the dictionaries.</typeparam>
+		/// <param name="handle">The pointer to the native NSArray instance containing NSDictionary objects.</param>
+		/// <param name="createObjectFromDictionary">A factory function that creates an instance of type T from an NSDictionary.</param>
+		/// <param name="releaseHandle">Whether the native NSArray instance should be released before returning or not. Defaults to false.</param>
+		/// <returns>A C# array with the values. Returns an empty array if the handle is zero. Null and NSNull elements are excluded from the result.</returns>
+		/// <remarks>
+		///   <para>This method is a wrapper around <see cref="DictionaryArrayFromHandleDropNullElements{T}"/> that guarantees a non-null return value. If the handle is zero or null, an empty array is returned instead of null.</para>
+		/// </remarks>
+		internal static T [] NonNullDictionaryArrayFromHandleDropNullElements<T> (NativeHandle handle, Func<NSDictionary, T> createObjectFromDictionary, bool releaseHandle = false)
+		{
+			var rv = DictionaryArrayFromHandleDropNullElements<T> (handle, createObjectFromDictionary, releaseHandle);
+			if (rv is null)
+				return Array.Empty<T> ();
+			return rv;
+		}
+#nullable disable
+
 		/// <typeparam name="T">Parameter type, determines the kind of array returned.</typeparam>
 		/// <param name="handle">Pointer (handle) to the unmanaged object.</param>
 		/// <param name="creator">Method that can create objects of type T from a given IntPtr.</param>

src/VideoToolbox/VTVideoEncoder.cs

@@ -35,13 +35,7 @@ public class VTVideoEncoder {
 					return null;
 			}
 
-			var dicts = NSArray.ArrayFromHandle<NSDictionary> (array);
-			var ret = new VTVideoEncoder [dicts.Length];
-			int i = 0;
-			foreach (var dict in dicts)
-				ret [i++] = new VTVideoEncoder (dict);
-			CFObject.CFRelease (array);
-			return ret;
+			return NSArray.DictionaryArrayFromHandleDropNullElements<VTVideoEncoder> (array, dict => new VTVideoEncoder (dict), releaseHandle: true);
 		}
 
 		/// <summary>To be added.</summary>

tests/monotouch-test/CoreText/FontTest.cs

@@ -163,5 +163,16 @@ class AdaptiveImageProvider : NSObject, ICTAdaptiveImageProviding {
 				return null;
 			}
 		}
+
+		[Test]
+		public void GetVariationAxes ()
+		{
+			using (var font = new CTFont ("HoeflerText-Regular", 10)) {
+				var axes = font.GetVariationAxes ();
+				Assert.IsNotNull (axes, "axes");
+				// HoeflerText-Regular has no variation axes, so we expect an empty array
+				Assert.That (axes.Length, Is.EqualTo (0), "Length");
+			}
+		}
 	}
 }