[ios, macos] Add mgl_coalesce: as expression function.

3 files changed, 11 insertions, 12 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 23ba0d87fe..2ff0d100f6 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -60,6 +60,7 @@
     INSTALL_METHOD(mgl_join:);
     INSTALL_METHOD(mgl_interpolate:withCurveType:parameters:stops:);
     INSTALL_METHOD(mgl_step:from:stops:);
+    INSTALL_METHOD(mgl_coalesce:);
     
     // Install functions that resemble control structures, taking arbitrary
     // numbers of arguments. Vararg aftermarket functions need to be declared
@@ -99,6 +100,12 @@
     return nil;
 }
 
+- (id)mgl_coalesce:(NSArray<NSExpression *> *)elements {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Coalesce expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 /**
  A placeholder for a method that evaluates an expression based on an arbitrary
  number of variable names and assigned expressions.
@@ -399,12 +406,6 @@
     return [self valueForKeyPath:@"mgl_jsonExpressionObject"];
 }
 
-- (id)mgl_coalesce {
-    [NSException raise:NSInvalidArgumentException
-                format:@"Coalesce expressions lack underlying Objective-C implementations."];
-    return nil;
-}
-
 @end
 
 @implementation NSDictionary (MGLExpressionAdditions)
@@ -663,7 +664,7 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 [expressions addObject:[NSExpression mgl_expressionWithJSONObject:operand]];
             }
             
-            return [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_coalesce')", expressions];
+            return [NSExpression expressionWithFormat:@"mgl_coalesce(%@)", expressions];
         } else {
             NSArray *subexpressions = MGLSubexpressionsWithJSONObjects(array);
             return [NSExpression expressionForFunction:@"MGL_FUNCTION" arguments:subexpressions];
@@ -873,10 +874,10 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }
                 
                 return expressionObject;
-            } else if ([function isEqualToString:@"mgl_coalesce"]) {
+            } else if ([function isEqualToString:@"mgl_coalesce:"]) {
                 NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"coalesce", nil];
                 
-                for (NSExpression *expression in self.operand.constantValue) {
+                for (NSExpression *expression in self.arguments.firstObject.constantValue) {
                     [expressionObject addObject:[expression mgl_jsonExpressionObject]];
                 }
                 
diff --git a/platform/darwin/src/NSExpression+MGLPrivateAdditions.h b/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
index f726dd3e71..d255cfdb0f 100644
--- a/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLPrivateAdditions.h
@@ -54,8 +54,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, readonly) id mgl_jsonExpressionObject;
 
-@property (nonatomic, readonly) id mgl_coalesce;
-
 @end
 
 @interface NSDictionary (MGLExpressionAdditions)
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index bfb1a2edc5..f00ea690f5 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -646,7 +646,7 @@ using namespace std::string_literals;
 
 - (void)testCoalesceExpressionObject {
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_coalesce')",
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_coalesce(%@)",
                                     @[[NSExpression expressionForKeyPath:@"x"],
                                       [NSExpression expressionForKeyPath:@"y"],
                                       [NSExpression expressionForKeyPath:@"z"],