NSExpression(MGLAdditions)

 
@interface NSExpression (MGLAdditions)

Methods for creating expressions that use Mapbox-specific functionality and for converting to and from the JSON format defined in the Mapbox Style Specification.

Creating Variable Expressions

  • NSExpression variable that corresponds to the zoom expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull zoomLevelVariableExpression;

    Swift

    class var zoomLevelVariable: NSExpression { get }
    View Source on GitHub

  • NSExpression variable that corresponds to the heatmap-density expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull heatmapDensityVariableExpression;

    Swift

    class var heatmapDensityVariable: NSExpression { get }
    View Source on GitHub

  • NSExpression variable that corresponds to the line-progress expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull lineProgressVariableExpression;

    Swift

    class var lineProgressVariable: NSExpression { get }
    View Source on GitHub

  • NSExpression variable that corresponds to the geometry-type expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull geometryTypeVariableExpression;

    Swift

    class var geometryTypeVariable: NSExpression { get }
    View Source on GitHub

  • NSExpression variable that corresponds to the id expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull featureIdentifierVariableExpression;

    Swift

    class var featureIdentifierVariable: NSExpression { get }
    View Source on GitHub

  • NSExpression variable that corresponds to the properties expression operator in the Mapbox Style Specification.

    Declaration

    Objective-C

    @property (readonly, nonatomic, class)
    NSExpression *_Nonnull featureAttributesVariableExpression;

    Swift

    class var featureAttributesVariable: NSExpression { get }
    View Source on GitHub

Creating Conditional Expressions

  • Returns a conditional function expression specifying the string predicate, and expressions for each condition.

    Declaration

    Objective-C

    + (nonnull instancetype)
    mgl_expressionForConditional:(nonnull NSPredicate *)conditionPredicate
                  trueExpression:(nonnull NSExpression *)trueExpression
                falseExpresssion:(nonnull NSExpression *)falseExpression;

    Swift

    convenience init(forMGLConditional conditionPredicate: NSPredicate, trueExpression: NSExpression, falseExpression: NSExpression)

    Parameters

    conditionPredicate

    The predicate to get evaluated.
    trueExpression

    The expression for conditions equal to true.
    falseExpression

    The expression for conditions equal to false.
    View Source on GitHub

Creating Ramp, Scale, and Curve Expressions

  • Returns a step function expression specifying the stepping, from expression and stops.

    See the Data-driven circles, Cluster point data, and Use images to cluster point data examples to learn how to use this expression to style a map layer based on an attribute value.

    Declaration

    Objective-C

    + (nonnull instancetype)
    mgl_expressionForSteppingExpression:
        (nonnull NSExpression *)steppingExpression
                         fromExpression:
                             (nonnull NSExpression *)minimumExpression
                                  stops:(nonnull NSExpression *)stops;

    Swift

    convenience init(forMGLStepping steppingExpression: NSExpression, from minimumExpression: NSExpression, stops: NSExpression)

    Parameters

    steppingExpression

    The stepping expression.
    minimumExpression

    The expression which could be a constant or function expression.
    stops

    The stops must be an NSDictionary constant NSExpression.
    View Source on GitHub

  • Returns an interpolated function expression specifying the function operator, curve type, parameters and steps.

    See the Create a heatmap layer example to learn how to style an MGLHeatmapStyleLayer based on zoom level and point density with this expression.

    Declaration

    Objective-C

    + (nonnull instancetype)
    mgl_expressionForInterpolatingExpression:
        (nonnull NSExpression *)inputExpression
                               withCurveType:
                                   (nonnull MGLExpressionInterpolationMode)
                                       curveType
                                  parameters:(nullable NSExpression *)parameters
                                       stops:(nonnull NSExpression *)stops;

    Swift

    convenience init(forMGLInterpolating inputExpression: NSExpression, curveType: MGLExpressionInterpolationMode, parameters: NSExpression?, stops: NSExpression)

    Parameters

    inputExpression

    The interpolating expression input.
    curveType
    parameters

    The parameters expression.
    stops

    The stops expression.
    View Source on GitHub

  • Returns a match function expression specifying the input, matching values, and default value.

    Declaration

    Objective-C

    + (nonnull instancetype)
    mgl_expressionForMatchingExpression:(nonnull NSExpression *)inputExpression
                           inDictionary:(nonnull NSDictionary<NSExpression *,
                                                              NSExpression *> *)
                                            matchedExpressions
                      defaultExpression:
                          (nonnull NSExpression *)defaultExpression;

    Swift

    convenience init(forMGLMatchingKey inputExpression: NSExpression, in matchedExpressions: [NSExpression : NSExpression], default defaultExpression: NSExpression)

    Parameters

    inputExpression

    The matching expression.
    matchedExpressions

    The matched values expression dictionary must be condition : value.
    defaultExpression

    The defaultValue expression to be used in case there is no match.
    View Source on GitHub

  • Returns an attributed function expression specifying an MGLAttributedExpression constant expression array.

    Declaration

    Objective-C

    + (nonnull instancetype)mgl_expressionForAttributedExpressions:
    (nonnull NSArray<NSExpression *> *)attributedExpressions;

    Swift

    convenience init(forAttributedExpressions attributedExpressions: [NSExpression])

    Parameters

    attributedExpressions

    The MGLAttributedExpression constant expression array.
    View Source on GitHub

Concatenating String Expressions

  • Returns a constant expression appending the passed expression.

    Note

    Both the receiver and the given expression must be an NSString constant expression type; otherwise, an exception is rised.

    Declaration

    Objective-C

    - (nonnull instancetype)mgl_expressionByAppendingExpression:
    (nonnull NSExpression *)expression;

    Swift

    func mgl_appending(_ expression: NSExpression) -> Self

    Parameters

    expression

    The expression to append to the receiver.
    View Source on GitHub

Converting JSON Expressions

  • Returns an expression equivalent to the given Foundation object deserialized from JSON data.

    The Foundation object is interpreted according to the Mapbox Style Specification. See the “Information for Style Authors” guide for a correspondence of operators and types between the style specification and the NSExpression representation used by this SDK.

    Declaration

    Objective-C

    + (nonnull instancetype)expressionWithMGLJSONObject:(nonnull id)object;

    Swift

    convenience init(mglJSONObject object: Any)

    Parameters

    object

    A Foundation object deserialized from JSON data, for example using NSJSONSerialization.

    Return Value

    An initialized expression equivalent to object, suitable for use as the value of a style layer attribute.

    View Source on GitHub

  • An equivalent Foundation object that can be serialized as JSON.

    The Foundation object conforms to the Mapbox Style Specification. See the “Information for Style Authors” guide for a correspondence of operators and types between the style specification and the NSExpression representation used by this SDK.

    You can use NSJSONSerialization to serialize the Foundation object as data to write to a file.

    Declaration

    Objective-C

    @property (readonly, nonatomic) id _Nonnull mgl_jsonExpressionObject;

    Swift

    var mgl_jsonExpressionObject: Any { get }
    View Source on GitHub

Localizing the Expression

  • Returns a copy of the receiver localized into the given locale.

    This method assumes the receiver refers to the feature attributes that are available in vector tiles supplied by the Mapbox Streets source. On iOS, the user can set the system’s preferred language in Settings, General Settings, Language & Region. On macOS, the user can set the system’s preferred language in the Language & Region pane of System Preferences.

    Declaration

    Objective-C

    - (nonnull NSExpression *)mgl_expressionLocalizedIntoLocale:
    (nullable NSLocale *)locale;

    Swift

    func mgl_expressionLocalized(into locale: Locale?) -> NSExpression

    Parameters

    locale

    The locale into which labels should be localized. To use the system’s preferred language, if supported, specify nil. To use the local language, specify a locale with the identifier mul.
    View Source on GitHub