rebase and improve PR #741 - ReadGroups

QuickFIXn/Message/FieldMap.cs

@@ -657,22 +657,39 @@ public List<int> GetGroupTags()
             return new List<int>(_groups.Keys);
         }
 
-        #region IEnumerable<KeyValuePair<int,IField>> Members
+        /// <summary>
+        /// Read groups via IEnumerable.
+        /// </summary>
+        /// <typeparam name="TGroup">The group class type retrieved by groupCountTag</typeparam>
+        /// <param name="groupCountTag">The FIX group tag</param>
+        /// <returns>retrieved enumerable groups</returns>
+        /// <exception cref="InvalidCastException">If groupCountTag retreives a group that can't be cast to TGroup</exception>
+        public IEnumerable<TGroup> ReadGroups<TGroup>(int groupCountTag) where TGroup : Group
+        {
+            if (IsSetField(groupCountTag) && GetGroupTags().Contains(groupCountTag))
+            {
+                int grpCount = GetInt(groupCountTag);
+
+                for (int grpIndex = 1; grpIndex <= grpCount; grpIndex += 1)
+                {
+                    Group group = GetGroup(grpIndex, groupCountTag);
+                    if(group is not TGroup tgroup)
+                        throw new InvalidCastException($"Can't cast {group.GetType()} to {typeof(TGroup)}");
+                    yield return tgroup;
+                }
+            }
+        }
 
+        // IEnumerable<KeyValuePair<int,IField>> Member
         public IEnumerator<KeyValuePair<int, IField>> GetEnumerator()
         {
             return _fields.GetEnumerator();
         }
 
-        #endregion
-
-        #region IEnumerable Members
-
+        // IEnumerable Member
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
         {
             return _fields.GetEnumerator();
         }
-
-        #endregion
     }
 }

RELEASE_NOTES.md

@@ -48,6 +48,7 @@ What's New
 * #907 - A fix to make body-less messages work, specifically 35=n aka XMLnonFIX (gbirchmeier)
 * #910 - faster Message.GetMsgType that doesn't use Regex (jkulubya)
 * #516 - remove ability to toggle Session-enable via HttpServer because it never really worked (gbirchmeier)
+* #913/#741 - new FieldMap.ReadGroups for iterating on groups (NoviProg/gbirchmeier)
 
 ### v1.12.0
 

UnitTests/FieldMap_ReadGroupsTests.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Linq;
+using NUnit.Framework;
+using QuickFix.FIX42;
+using QuickFix.Fields;
+
+namespace UnitTests;
+
+[TestFixture]
+public class FieldMap_ReadGroupsTests {
+    public class GroupExtensionTest
+    {
+        private static News CreateNewsForTest(int numberOfLines) {
+            News msg = new();
+            msg.Headline = new Headline("Blah headline");
+            for (int i = 0; i < numberOfLines; i++) {
+                News.LinesOfTextGroup grp = new();
+                grp.SetField(new Text($"OHHAI_{i}"));
+                msg.AddGroup(grp);
+            }
+            return msg;
+        }
+
+        [Test]
+        public void ReadGroups_NormalScenario() {
+            News msg = CreateNewsForTest(10);
+            int iterCount = 0;
+            foreach (News.LinesOfTextGroup item in msg.ReadGroups<News.LinesOfTextGroup>(Tags.NoLinesOfText))
+                Assert.That(item.Text.Value, Is.EqualTo($"OHHAI_{iterCount++}"));
+            Assert.That(iterCount == 10);
+        }
+
+        [Test]
+        public void ReadGroups_ZeroCount() {
+            News msg = new();
+            Assert.That(msg.ReadGroups<News.LinesOfTextGroup>(Tags.NoLinesOfText).ToList(), Is.Empty);
+        }
+
+        [Test]
+        public void ReadGroups_WrongTag() {
+            // Tag doesn't match the templated group
+            // case 1: incorrect tag is not present in message
+            News msg = CreateNewsForTest(3);
+            Assert.That(msg.IsSetField(Tags.Account), Is.False);
+            Assert.That(msg.ReadGroups<News.LinesOfTextGroup>(Tags.Account).ToList(), Is.Empty);
+
+            // case 2: incorrect tag present but value isn't an int (like a group counter would be)
+            Assert.That(msg.IsSetHeadline());
+            Assert.That(msg.ReadGroups<News.LinesOfTextGroup>(Tags.Headline).ToList(), Is.Empty);
+
+            // case 3: incorrect tag present and an int, but isn't group counter at all
+            msg.SetField(new RawDataLength(100));
+            Assert.That(msg.ReadGroups<News.LinesOfTextGroup>(Tags.RawDataLength).ToList(), Is.Empty);
+        }
+
+        [Test]
+        public void ReadGroups_WrongGroup() {
+            // The tag is good, but the template type is incorrect
+            // Case 1: The tag's group is empty, so the templated type doesn't matter.
+            News msg = CreateNewsForTest(0);
+            Assert.That(msg.ReadGroups<QuickFix.FIX44.ExecutionReport.NoLegsGroup>(Tags.NoLinesOfText).ToList(),
+                Is.Empty);
+
+            // Case 2: Group is not empty, so InvalidCastException will occur
+            msg = CreateNewsForTest(1);
+            var ex = Assert.Throws<InvalidCastException>(
+                () => msg.ReadGroups<QuickFix.FIX44.ExecutionReport.NoLegsGroup>(Tags.NoLinesOfText).ToList());
+            Assert.That(ex!.Message, Is.EqualTo("Can't cast QuickFix.FIX42.News+LinesOfTextGroup to QuickFix.FIX44.ExecutionReport+NoLegsGroup"));
+        }
+    }
+}