[ios, macos] Add convenience initializers to shape source (#7665)

This adds two new convenience initializers to MGLShapeSource:

-initWithIdentifier:features:options: takes an array of shape objects
that conform to MGLFeature, inserts them in a shape collection feature
and creates a source with that shape. -initWithIdentifier:shapes:options
does the same but with concrete MGLShape objects that get added to
a shape collection.

Throw an exception if an shape source is created with the features
initializer but is sent an array of features that contains something
that is not actually an object that conforms to the feature protocol.

Updates to geojson data guide

Qualify APIs that take arrays of shapes that are features

1 files changed, 10 insertions, 0 deletions

diff --git a/platform/darwin/docs/guides/Working with GeoJSON Data.md b/platform/darwin/docs/guides/Working with GeoJSON Data.md
index 0fffed06dd..adaf053e41 100644
--- a/platform/darwin/docs/guides/Working with GeoJSON Data.md
+++ b/platform/darwin/docs/guides/Working with GeoJSON Data.md
@@ -36,6 +36,16 @@ resulting shape or feature object into the
 the map, or you can use the object and its properties to power non-map-related
 functionality in your application.
 
+To include multiple shapes in the source, create and pass an `MGLShapeCollection` or
+ `MGLShapeCollectionFeature` object to 
+ `-[MGLShapeSource initWithIdentifier:shape:options:]`. Alternatively, use the
+ `-[MGLShapeSource initWithIdentifier:features:options:]` or 
+ `-[MGLShapeSource initWithIdentifier:shapes:options:]` method to create a shape source 
+ with an array. `-[MGLShapeSource initWithIdentifier:features:options:]` accepts only `MGLFeature`
+ instances, such as `MGLPointFeature` objects, whose attributes you can use when
+ applying a predicate to `MGLVectorStyleLayer` or configuring a style layer’s
+ appearance.
+
 ## Extracting GeoJSON data from the map
 
 Any `MGLShape`, `MGLFeature`, or `MGLShapeCollectionFeature` object has an