MGLCircleStyleLayer
@interface MGLCircleStyleLayer : MGLVectorStyleLayer
An MGLCircleStyleLayer
is a style layer that renders one or more filled
circles on the map.
Use a circle style layer to configure the visual appearance of point or point
collection features. These features can come from vector tiles loaded by an
MGLVectorTileSource
object, or they can be MGLPointAnnotation
,
MGLPointFeature
, MGLPointCollection
, or MGLPointCollectionFeature
instances in an MGLShapeSource
or MGLComputedShapeSource
object.
A circle style layer renders circles whose radii are measured in screen units.
To display circles on the map whose radii correspond to real-world distances,
use many-sided regular polygons and configure their appearance using an
MGLFillStyleLayer
object.
You can access an existing circle style layer using the
-[MGLStyle layerWithIdentifier:]
method if you know its identifier;
otherwise, find it using the MGLStyle.layers
property. You can also create a
new circle style layer and add it to the style using a method such as
-[MGLStyle addLayer:]
.
Related examples
See the Data-driven circles, Add multiple shapes from a single shape source, and Cluster point data examples to learn how to add circles to your map using this style layer.
Example
let layer = MGLCircleStyleLayer(identifier: "circles", source: population)
layer.sourceLayerIdentifier = "population"
layer.circleColor = NSExpression(forConstantValue: UIColor.green)
layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.75, %@)",
[12: 2,
22: 180])
layer.circleOpacity = NSExpression(forConstantValue: 0.7)
layer.predicate = NSPredicate(format: "%K == %@", "marital-status", "married")
mapView.style?.addLayer(layer)
-
Returns a circle style layer initialized with an identifier and source.
After initializing and configuring the style layer, add it to a map view’s style using the
-[MGLStyle addLayer:]
or-[MGLStyle insertLayer:belowLayer:]
method.Declaration
Objective-C
- (nonnull instancetype)initWithIdentifier:(nonnull NSString *)identifier source:(nonnull MGLSource *)source;
Swift
init(identifier: String, source: MGLSource)
Parameters
identifier
A string that uniquely identifies the source in the style to which it is added.
source
The source from which to obtain the data to style. If the source has not yet been added to the current style, the behavior is undefined.
Return Value
An initialized foreground style layer.
-
Sorts features in ascending order based on this value. Features with a higher sort key will appear above features with a lower sort key.
You can set this property to an expression containing any of the following:
- Constant numeric values
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleSortKey;
Swift
var circleSortKey: NSExpression! { get set }
-
Amount to blur the circle. 1 blurs the circle such that only the centerpoint is full opacity.
The default value of this property is an expression that evaluates to the float
0
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant numeric values
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleBlur;
Swift
var circleBlur: NSExpression! { get set }
-
The transition affecting any changes to this layer’s
circleBlur
property.This property corresponds to the
circle-blur-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleBlurTransition;
Swift
var circleBlurTransition: MGLTransition { get set }
-
The fill color of the circle.
The default value of this property is an expression that evaluates to
UIColor.blackColor
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant
UIColor
values - Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleColor;
Swift
var circleColor: NSExpression! { get set }
- Constant
-
The transition affecting any changes to this layer’s
circleColor
property.This property corresponds to the
circle-color-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleColorTransition;
Swift
var circleColorTransition: MGLTransition { get set }
-
The opacity at which the circle will be drawn.
The default value of this property is an expression that evaluates to the float
1
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant numeric values between 0 and 1 inclusive
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleOpacity;
Swift
var circleOpacity: NSExpression! { get set }
-
The transition affecting any changes to this layer’s
circleOpacity
property.This property corresponds to the
circle-opacity-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleOpacityTransition;
Swift
var circleOpacityTransition: MGLTransition { get set }
-
Orientation of circle when map is pitched.
The default value of this property is an expression that evaluates to
viewport
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant
MGLCirclePitchAlignment
values - Any of the following constant string values:
map
: The circle is aligned to the plane of the map.viewport
: The circle is aligned to the plane of the viewport.
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Step functions applied to the
$zoomLevel
variable
This property does not support applying interpolation functions to the
$zoomLevel
variable or applying interpolation or step functions to feature attributes.Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circlePitchAlignment;
Swift
var circlePitchAlignment: NSExpression! { get set }
- Constant
-
Circle radius.
This property is measured in points.
The default value of this property is an expression that evaluates to the float
5
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant numeric values no less than 0
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleRadius;
Swift
var circleRadius: NSExpression! { get set }
-
The transition affecting any changes to this layer’s
circleRadius
property.This property corresponds to the
circle-radius-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleRadiusTransition;
Swift
var circleRadiusTransition: MGLTransition { get set }
-
Controls the scaling behavior of the circle when the map is pitched.
The default value of this property is an expression that evaluates to
map
. Set this property tonil
to reset it to the default value.This attribute corresponds to the
circle-pitch-scale
layout property in the Mapbox Style Specification.You can set this property to an expression containing any of the following:
- Constant
MGLCircleScaleAlignment
values - Any of the following constant string values:
map
: Circles are scaled according to their apparent distance to the camera.viewport
: Circles are not scaled.
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Step functions applied to the
$zoomLevel
variable
This property does not support applying interpolation functions to the
$zoomLevel
variable or applying interpolation or step functions to feature attributes.Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleScaleAlignment;
Swift
var circleScaleAlignment: NSExpression! { get set }
- Constant
-
The stroke color of the circle.
The default value of this property is an expression that evaluates to
UIColor.blackColor
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant
UIColor
values - Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleStrokeColor;
Swift
var circleStrokeColor: NSExpression! { get set }
- Constant
-
The transition affecting any changes to this layer’s
circleStrokeColor
property.This property corresponds to the
circle-stroke-color-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleStrokeColorTransition;
Swift
var circleStrokeColorTransition: MGLTransition { get set }
-
The opacity of the circle’s stroke.
The default value of this property is an expression that evaluates to the float
1
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant numeric values between 0 and 1 inclusive
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleStrokeOpacity;
Swift
var circleStrokeOpacity: NSExpression! { get set }
-
The transition affecting any changes to this layer’s
circleStrokeOpacity
property.This property corresponds to the
circle-stroke-opacity-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleStrokeOpacityTransition;
Swift
var circleStrokeOpacityTransition: MGLTransition { get set }
-
The width of the circle’s stroke. Strokes are placed outside of the
circleRadius
.This property is measured in points.
The default value of this property is an expression that evaluates to the float
0
. Set this property tonil
to reset it to the default value.You can set this property to an expression containing any of the following:
- Constant numeric values no less than 0
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable and/or feature attributes
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleStrokeWidth;
Swift
var circleStrokeWidth: NSExpression! { get set }
-
The transition affecting any changes to this layer’s
circleStrokeWidth
property.This property corresponds to the
circle-stroke-width-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleStrokeWidthTransition;
Swift
var circleStrokeWidthTransition: MGLTransition { get set }
-
The geometry’s offset.
This property is measured in points.
The default value of this property is an expression that evaluates to an
NSValue
object containing aCGVector
struct set to 0 points rightward and 0 points downward. Set this property tonil
to reset it to the default value.This attribute corresponds to the
circle-translate
layout property in the Mapbox Style Specification.You can set this property to an expression containing any of the following:
- Constant
CGVector
values - Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Interpolation and step functions applied to the
$zoomLevel
variable
This property does not support applying interpolation or step functions to feature attributes.
Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleTranslation;
Swift
var circleTranslation: NSExpression! { get set }
- Constant
-
The transition affecting any changes to this layer’s
circleTranslation
property.This property corresponds to the
circle-translate-transition
property in the style JSON file format.Declaration
Objective-C
@property (assign, readwrite, nonatomic) MGLTransition circleTranslationTransition;
Swift
var circleTranslationTransition: MGLTransition { get set }
-
Controls the frame of reference for
circleTranslation
.The default value of this property is an expression that evaluates to
map
. Set this property tonil
to reset it to the default value.This property is only applied to the style if
circleTranslation
is non-nil
. Otherwise, it is ignored.This attribute corresponds to the
circle-translate-anchor
layout property in the Mapbox Style Specification.You can set this property to an expression containing any of the following:
- Constant
MGLCircleTranslationAnchor
values - Any of the following constant string values:
map
: The circle is translated relative to the map.viewport
: The circle is translated relative to the viewport.
- Predefined functions, including mathematical and string operators
- Conditional expressions
- Variable assignments and references to assigned variables
- Step functions applied to the
$zoomLevel
variable
This property does not support applying interpolation functions to the
$zoomLevel
variable or applying interpolation or step functions to feature attributes.Declaration
Objective-C
@property (assign, readwrite, nonatomic, null_resettable) NSExpression *circleTranslationAnchor;
Swift
var circleTranslationAnchor: NSExpression! { get set }
- Constant