Move creation of FSTFilter objects to static create method on FSTFilter. (#1512)

Rather than previously inlining it in the calling code. This is to unify
filter creation across platforms.

(This change involves altering FSTFilter from a protocol to an abstract
class.)

1 files changed, 6 insertions, 19 deletions

diff --git a/Firestore/Source/API/FIRQuery.mm b/Firestore/Source/API/FIRQuery.mm
index 08c912d..cdf8bc9 100644
--- a/Firestore/Source/API/FIRQuery.mm
+++ b/Firestore/Source/API/FIRQuery.mm
@@ -487,26 +487,13 @@ addSnapshotListenerInternalWithOptions:(FSTListenOptions *)internalOptions
     fieldValue = [self.firestore.dataConverter parsedQueryValue:value];
   }
 
-  id<FSTFilter> filter;
-  if ([fieldValue isEqual:[FSTNullValue nullValue]]) {
-    if (filterOperator != FSTRelationFilterOperatorEqual) {
-      FSTThrowInvalidUsage(@"InvalidQueryException",
-                           @"Invalid Query. You can only perform equality comparisons on nil / "
-                            "NSNull.");
-    }
-    filter = [[FSTNullFilter alloc] initWithField:fieldPath];
-  } else if ([fieldValue isEqual:[FSTDoubleValue nanValue]]) {
-    if (filterOperator != FSTRelationFilterOperatorEqual) {
-      FSTThrowInvalidUsage(@"InvalidQueryException",
-                           @"Invalid Query. You can only perform equality comparisons on NaN.");
-    }
-    filter = [[FSTNanFilter alloc] initWithField:fieldPath];
-  } else {
-    filter = [FSTRelationFilter filterWithField:fieldPath
-                                 filterOperator:filterOperator
-                                          value:fieldValue];
-    [self validateNewRelationFilter:filter];
+  FSTFilter *filter =
+      [FSTFilter filterWithField:fieldPath filterOperator:filterOperator value:fieldValue];
+
+  if ([filter isKindOfClass:[FSTRelationFilter class]]) {
+    [self validateNewRelationFilter:(FSTRelationFilter *)filter];
   }
+
   return [FIRQuery referenceWithQuery:[self.query queryByAddingFilter:filter]
                             firestore:self.firestore];
 }