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Diffstat (limited to 'platform/macos/docs/guides/For Style Authors.md')
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1 files changed, 80 insertions, 42 deletions
diff --git a/platform/macos/docs/guides/For Style Authors.md b/platform/macos/docs/guides/For Style Authors.md index 9eeb159b75..4a16066a2a 100644 --- a/platform/macos/docs/guides/For Style Authors.md +++ b/platform/macos/docs/guides/For Style Authors.md @@ -257,12 +257,16 @@ In style JSON | In Objective-C | In Swift ## Setting attribute values Each property representing a layout or paint attribute is set to an -`MGLStyleValue` object, which is either an `MGLConstantStyleValue` object (for -constant values) or an `MGLStyleFunction` object (for style functions). The -style value object is a container for the raw value or function parameters that -you want the attribute to be set to. +`NSExpression` object. `NSExpression` objects play the same role as +[expressions in the Mapbox Style Specification](https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions), +but you create the former using a very different syntax. `NSExpression`’s format +string syntax is reminiscent of a spreadsheet formula or an expression in a +database query. See the +“[Predicates and Expressions](Predicates and Expressions.md)” guide for an +overview of the expression support in this SDK. This SDK no longer supports +style functions; use expressions instead. -### Constant style values +### Constant values in expressions In contrast to the JSON type that the style specification defines for each layout or paint property, the style value object often contains a more specific @@ -273,10 +277,10 @@ or set. In style JSON | In Objective-C | In Swift --------------|-----------------------|--------- Color | `NSColor` | `NSColor` -Enum | `NSValue` (see `NSValue(MGLAdditions)`) | `NSValue` (see `NSValue(MGLAdditions)`) +Enum | `NSString` | `String` String | `NSString` | `String` -Boolean | `NSNumber.boolValue` | `Bool` -Number | `NSNumber.floatValue` | `Float` +Boolean | `NSNumber.boolValue` | `NSNumber.boolValue` +Number | `NSNumber.floatValue` | `NSNumber.floatValue` Array (`-dasharray`) | `NSArray<NSNumber>` | `[Float]` Array (`-font`) | `NSArray<NSString>` | `[String]` Array (`-offset`, `-translate`) | `NSValue` containing `CGVector` | `NSValue` containing `CGVector` @@ -294,38 +298,72 @@ offset or translation upward, while a negative `CGVector.dy` means an offset or translation downward. This is the reverse of how `CGVector` is interpreted on iOS. -### Style functions - -A _style function_ allows you to vary the value of a layout or paint attribute -based on the zoom level, data provided by content sources, or both. For more -information about style functions, see “[Using Style Functions at Runtime](using-style-functions-at-runtime.html)”. - -Each kind of style function is represented by a distinct class, but you -typically create style functions as you create any other style value, using -class methods on `MGLStyleValue`: - -In style specification | SDK class | SDK factory method ----------------------------|-----------------------------|------------------- -zoom function | `MGLCameraStyleFunction` | `+[MGLStyleValue valueWithInterpolationMode:cameraStops:options:]` -property function | `MGLSourceStyleFunction` | `+[MGLStyleValue valueWithInterpolationMode:sourceStops:attributeName:options:]` -zoom-and-property function | `MGLCompositeStyleFunction` | `+[MGLStyleValue valueWithInterpolationMode:compositeStops:attributeName:options:]` - -The documentation for each individual style layer property indicates the kinds -of style functions that are enabled for that property. - -When you create a style function, you specify an _interpolation mode_ and a -series of _stops_. Each stop determines the effective value displayed at a -particular zoom level (for camera functions) or the effective value on features -with a particular attribute value in the content source (for source functions). -The interpolation mode tells the SDK how to calculate the effective value -between any two stops: - -In style specification | In the SDK ------------------------------|----------- -`exponential` | `MGLInterpolationModeExponential` -`interval` | `MGLInterpolationModeInterval` -`categorical` | `MGLInterpolationModeCategorical` -`identity` | `MGLInterpolationModeIdentity` +### Expression operators + +In style specification | Method, function, or predicate type | Format string syntax +-----------------------|-------------------------------------|--------------------- +`array` | | +`boolean` | | +`literal` | `+[NSExpression expressionForConstantValue:]` | `%@` representing `NSArray` or `NSDictionary` +`number` | | +`string` | | +`to-boolean` | `boolValue` | +`to-color` | | +`to-number` | `mgl_numberWithFallbackValues:` | +`to-string` | `stringValue` | +`typeof` | | +`geometry-type` | | +`id` | | +`properties` | | +`at` | | +`get` | `+[NSExpression expressionForKeyPath:]` | Key path +`has` | | +`length` | `count:` | `count({1, 2, 2, 3, 4, 7, 9})` +`!` | `NSNotPredicateType` | `NOT (p0 OR … OR pn)` +`!=` | `NSNotEqualToPredicateOperatorType` | `key != value` +`<` | `NSLessThanPredicateOperatorType` | `key < value` +`<=` | `NSLessThanOrEqualToPredicateOperatorType` | `key <= value` +`==` | `NSEqualToPredicateOperatorType` | `key == value` +`>` | `NSGreaterThanPredicateOperatorType` | `key > value` +`>=` | `NSGreaterThanOrEqualToPredicateOperatorType` | `key >= value` +`all` | `NSAndPredicateType` | `p0 AND … AND pn` +`any` | `NSOrPredicateType` | `p0 OR … OR pn` +`case` | `+[NSExpression expressionForConditional:trueExpression:falseExpression:]` | `TERNARY(condition, trueExpression, falseExpression)` +`coalesce` | | +`match` | | +`interpolate` | `mgl_interpolateWithCurveType:parameters:stops:` | +`step` | `mgl_stepWithMinimum:stops:` | +`let` | `mgl_expressionWithContext:` | +`var` | `+[NSExpression expressionForVariable:]` | `$variable` +`concat` | `stringByAppendingString:` | +`downcase` | `lowercase:` | `lowercase('DOWNTOWN')` +`upcase` | `uppercase:` | `uppercase('Elysian Fields')` +`rgb` | `+[NSColor colorWithCalibratedRed:green:blue:alpha:]` | +`rgba` | `+[NSColor colorWithCalibratedRed:green:blue:alpha:]` | +`to-rgba` | | +`-` | `from:subtract:` | `2 - 1` +`*` | `multiply:by:` | `1 * 2` +`/` | `divide:by:` | `1 / 2` +`%` | `modulus:by:` | +`^` | `raise:toPower:` | `2 ** 2` +`+` | `add:to:` | `1 + 2` +`acos` | | +`asin` | | +`atan` | | +`cos` | | +`e` | | `%@` representing `NSNumber` containing `M_E` +`ln` | `ln:` | `ln(2)` +`ln2` | | `%@` representing `NSNumber` containing `M_LN2` +`log10` | `log:` | `log(1)` +`log2` | | +`max` | `max:` | `max({1, 2, 2, 3, 4, 7, 9})` +`min` | `min:` | `min({1, 2, 2, 3, 4, 7, 9})` +`pi` | | `%@` representing `NSNumber` containing `M_PI` +`sin` | | +`sqrt` | `sqrt:` | `sqrt(2)` +`tan` | | +`zoom` | | `$zoom` +`heatmap-density` | | `$heatmapDensity` ## Filtering sources @@ -350,5 +388,5 @@ In style JSON | In the format string `["any", f0, …, fn]` | `p0 OR … OR pn` `["none", f0, …, fn]` | `NOT (p0 OR … OR pn)` -See the `MGLVectorStyleLayer.predicate` documentation for a full description of -the supported operators and operand types. +See the “[Predicates and Expressions](Predicates and Expressions.md)” guide for +a full description of the supported operators and operand types. |