[ios, macos] Add MGL_SWITCH expression operator.

4 files changed, 33 insertions, 47 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 776aed642b..23ba0d87fe 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -66,6 +66,7 @@
     // with an explicit and implicit first argument.
     INSTALL_CONTROL_STRUCTURE(MGL_LET);
     INSTALL_CONTROL_STRUCTURE(MGL_MATCH);
+    INSTALL_CONTROL_STRUCTURE(MGL_SWITCH);
     INSTALL_CONTROL_STRUCTURE(MGL_FUNCTION);
     
     #undef INSTALL_AFTERMARKET_FN
@@ -118,6 +119,29 @@
 }
 
 /**
+ A placeholder for a method that evaluates an expression and returns the matching element.
+ */
+- (id)MGL_SWITCH:(id)firstCondition, ... {
+    va_list argumentList;
+    va_start(argumentList, firstCondition);
+    
+    for (id eachExpression = firstCondition; eachExpression; eachExpression = va_arg(argumentList, id)) {
+        if ([eachExpression isKindOfClass:[NSComparisonPredicate class]]) {
+            id valueExpression = va_arg(argumentList, id);
+            if ([eachExpression evaluateWithObject:nil]) {
+                return valueExpression;
+            }
+        } else {
+            return eachExpression;
+        }
+    }
+    va_end(argumentList);
+    
+    return nil;
+}
+
+
+/**
  A placeholder for a catch-all method that evaluates an arbitrary number of
  arguments as an expression according to the Mapbox Style Specification’s
  expression language.
@@ -610,21 +634,19 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
         } else if ([op isEqualToString:@"var"]) {
             return [NSExpression expressionForVariable:argumentObjects.firstObject];
         } else if ([op isEqualToString:@"case"]) {
-            NSArray *caseExpressions = argumentObjects;
-            NSExpression *firstConditional = [NSExpression expressionWithFormat:@"%@", [NSPredicate mgl_predicateWithJSONObject:caseExpressions[0]]];
             NSMutableArray *arguments = [NSMutableArray array];
             
-            for (NSUInteger index = 1; index < caseExpressions.count; index++) {
-                if ([caseExpressions[index] isKindOfClass:[NSArray class]]) {
-                    NSPredicate *conditional = [NSPredicate mgl_predicateWithJSONObject:caseExpressions[index]];
+            for (NSUInteger index = 0; index < argumentObjects.count; index++) {
+                if ([argumentObjects[index] isKindOfClass:[NSArray class]]) {
+                    NSPredicate *conditional = [NSPredicate mgl_predicateWithJSONObject:argumentObjects[index]];
                     NSExpression *argument = [NSExpression expressionWithFormat:@"%@", conditional];
                     [arguments addObject:argument];
                 } else {
-                    [arguments addObject:[NSExpression mgl_expressionWithJSONObject:caseExpressions[index]]];
+                    [arguments addObject:[NSExpression mgl_expressionWithJSONObject:argumentObjects[index]]];
                 }
             }
             
-            return [NSExpression expressionForFunction:firstConditional selectorName:@"mgl_case:" arguments:arguments];
+            return [NSExpression expressionForFunction:@"MGL_SWITCH" arguments:arguments];
         } else if ([op isEqualToString:@"match"]) {
             NSMutableArray *optionsArray = [NSMutableArray array];
             NSEnumerator *optionsEnumerator = argumentObjects.objectEnumerator;
@@ -829,9 +851,8 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }];
                 [expressionObject addObject:self.operand.mgl_jsonExpressionObject];
                 return expressionObject;
-            } else if ([function isEqualToString:@"mgl_case:"]) {
-                NSPredicate *firstConditional = (NSPredicate *)self.operand.constantValue;
-                NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"case", firstConditional.mgl_jsonExpressionObject, nil];
+            } else if ([function isEqualToString:@"MGL_SWITCH"]) {
+                NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"case", nil];
 
                 for (NSExpression *option in self.arguments) {
                     if ([option respondsToSelector:@selector(constantValue)] && [option.constantValue isKindOfClass:[NSComparisonPredicate class]]) {
diff --git a/platform/darwin/src/NSPredicate+MGLAdditions.h b/platform/darwin/src/NSPredicate+MGLAdditions.h
index a67c6ca005..89e9e65c64 100644
--- a/platform/darwin/src/NSPredicate+MGLAdditions.h
+++ b/platform/darwin/src/NSPredicate+MGLAdditions.h
@@ -16,8 +16,4 @@
 
 @property (nonatomic, readonly) id mgl_jsonExpressionObject;
 
-- (id)mgl_case:(id)firstValue, ...;
-
-- (id)mgl_match:(NSExpression *)firstCase, ...;
-
 @end
diff --git a/platform/darwin/src/NSPredicate+MGLAdditions.mm b/platform/darwin/src/NSPredicate+MGLAdditions.mm
index 1a7bb30a92..63c8307803 100644
--- a/platform/darwin/src/NSPredicate+MGLAdditions.mm
+++ b/platform/darwin/src/NSPredicate+MGLAdditions.mm
@@ -324,35 +324,4 @@ NSArray *MGLSubpredicatesWithJSONObjects(NSArray *objects) {
     return nil;
 }
 
-- (id)mgl_case:(id)firstValue, ... {
-
-    if ([self evaluateWithObject:nil]) {
-        return firstValue;
-    }
-    
-    id eachExpression;
-    va_list argumentList;
-    va_start(argumentList, firstValue);
-    
-    while ((eachExpression = va_arg(argumentList, id))) {
-        if ([eachExpression isKindOfClass:[NSComparisonPredicate class]]) {
-            id valueExpression = va_arg(argumentList, id);
-            if ([eachExpression evaluateWithObject:nil]) {
-                return valueExpression;
-            }
-        } else {
-            return eachExpression;
-        }
-    }
-    va_end(argumentList);
-    
-    return nil;
-}
-
-- (id)mgl_match:(NSExpression *)firstCase, ... {
-    [NSException raise:NSInvalidArgumentException
-                format:@"Match expressions lack underlying Objective-C implementations."];
-    return nil;
-}
-
 @end
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index 5fb36ccbb9..bfb1a2edc5 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -660,7 +660,7 @@ using namespace std::string_literals;
 
 - (void)testConditionalExpressionObject {
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_case:', %@, %@)",
+        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_SWITCH(%@, %@, %@)",
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 2"]],
                                     MGLConstantExpression(@YES),
                                     MGLConstantExpression(@NO)];
@@ -670,7 +670,7 @@ using namespace std::string_literals;
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:nil], @NO);
     }
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_case:', %@, %@, %@, %@)",
+        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_SWITCH(%@, %@, %@, %@, %@)",
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 2"]],
                                     MGLConstantExpression(@YES),
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 1"]],