[ios, macos] Add support for subscripting in expressions. #11770
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| if ([value isEqualToString:@"FIRST"]) { | ||
| index = [NSExpression expressionForConstantValue:@0].mgl_jsonExpressionObject; | ||
| } else if ([value isEqualToString:@"LAST"]) { | ||
| NSArray *array = self.arguments[0].constantValue; |
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The first argument isn’t necessarily a constant value; it could be an aggregate expression or perhaps a conditional expression. Instead, synthesize an expression of the form count(%@) - 1, where %@ is arguments[0]. Also add a unit test to exercise this case.
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There are tests for each case:
mapbox-gl-native/platform/darwin/test/MGLExpressionTests.mm
Lines 843 to 844 in 8de1490
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| index = [NSExpression expressionForConstantValue:@0].mgl_jsonExpressionObject; | ||
| } else if ([value isEqualToString:@"LAST"]) { | ||
| NSExpression *count = [NSExpression expressionWithFormat:@"count(%@) - 1", self.arguments[0]]; | ||
| id last = [count expressionValueWithObject:nil context:nil]; |
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What if the first argument is an expression like CAST(color, 'NSArray')? Casting a color to an array is unimplemented by default in NSExpression, so evaluating the expression will raise an exception. Instead, get the mgl_jsonExpressionObject of count itself, similar to how the SIZE case is implemented.
| index = [NSExpression expressionForConstantValue:@0].mgl_jsonExpressionObject; | ||
| } else if ([value isEqualToString:@"LAST"]) { | ||
| NSExpression *count = [NSExpression expressionWithFormat:@"count(%@) - 1", self.arguments[0]]; | ||
| index = count.mgl_jsonExpressionObject; |
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Consider inlining count here, because the variable name count is a bit misleading. (It’s the last index, not the count.)
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Fixes #11757