MBFunction (Geotools modules 28-SNAPSHOT API)

Object
- MBFunction

```
public class MBFunction
extends Object
```
MBFunction json wrapper, allowing conversion of function to a GeoTools Expression.
As of v0.41.0, data expressions are the preferred method for styling features based on zoom level or the feature's properties.
Each function is evaluated according type: MBFunction.FunctionType.IDENTITY, MBFunction.FunctionType.INTERVAL, MBFunction.FunctionType.CATEGORICAL, MBFunction.FunctionType.EXPONENTIAL.
We have several methods that intelligently review getType() and produce the correct expression:

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`MBFunction.FunctionCategory` Function category property, zoom, or property and zoom.
`static class`	`MBFunction.FunctionType` Optional type, one of identity, exponential, interval, categorical.

Field Summary

Fields
Modifier and Type Field and Description

protected JSONObject json

protected MBObjectParser parse

Fields
Modifier and Type	Field and Description
`protected JSONObject`	`json`
`protected MBObjectParser`	`parse`

Constructor Summary

Constructors
Constructor and Description

MBFunction(JSONObject json)

MBFunction(MBObjectParser parse, JSONObject json)

Constructors
Constructor and Description
`MBFunction(JSONObject json)`
`MBFunction(MBObjectParser parse, JSONObject json)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`EnumSet<MBFunction.FunctionCategory>`	`category()` Programmatically look at the structure of the function and determine if it is a Zoom function, Property function or Zoom-and-property functions.
`Expression`	`color()` GeoTools `Expression` from json definition that evaluates to a color, used for properties such as 'color' and 'fill-color'.
`Expression`	`enumeration(Class<? extends Enum<?>> enumeration)` GeoTools `Expression` from json definition that evaluates to the provided Enum, used for properties such as 'line-cap' and 'text-transform'.
`Expression`	`font()` GeoTools `Expression` from json definition that evaluates to a font string, used for 'text-font'.
`Expression`	`function(Class<?> clazz)` GeoTools `Expression` from json definition.
`Number`	`getBase()` (Optional) Number.
`Object`	`getDefault()` A value to serve as a fallback function result when a value isn't otherwise available.
`String`	`getProperty()` If specified, the function will take the specified feature property as an input.
`JSONArray`	`getStops()` Functions are defined in terms of input and output values.
`MBFunction.FunctionType`	`getType()` Access the function 'type', or null if not specified.
`MBFunction.FunctionType`	`getTypeWithDefault(Class<?> clazz)` Return the function type, falling back to the default function type for the provided `Class` if no function type is explicitly declared.
`boolean`	`isArrayFunction()` Returns true if this function's stop values are all arrays.
`Expression`	`numeric()` GeoTools `Expression` from json definition that evaluates to a numeric, used for properties such as 'line-width' and 'opacity'.
`List<MBFunction>`	`splitArrayFunction()` Splits an array function into multiple functions, one for each dimension in the function's stop value arrays.

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - parse
```
protected final MBObjectParser parse
```
  - json
```
protected final JSONObject json
```
- Constructor Detail
  - MBFunction
```
public MBFunction(JSONObject json)
```
  - MBFunction
```
public MBFunction(MBObjectParser parse,
                  JSONObject json)
```
- Method Detail
  - getType
```
public MBFunction.FunctionType getType()
```
    Access the function 'type', or null if not specified.
    Depending on the domain you are working with ( enumeration(Class), color(), enumeration(Class)} ) the default value to use is different. These functions check for null and use the appropriate setting.
    
    Returns:
    
    function type, or null if not defined.
  - getDefault
```
public Object getDefault()
```
    A value to serve as a fallback function result when a value isn't otherwise available. It is used in the following circumstances:
    - In categorical functions, when the feature value does not match any of the stop domain values.
    - In property and zoom-and-property functions, when a feature does not contain a value for the specified property.
    - In identity functions, when the feature value is not valid for the style property (for example, if the function is being used for a circle-color property but the feature property value is not a string or not a valid color).
    - In interval or exponential property and zoom-and-property functions, when the feature value is not numeric.
    If no default is provided, the style property's default is used in these circumstances.
    Returns:
    
    The function's default value, or null if none was provided.
  - getTypeWithDefault
```
public MBFunction.FunctionType getTypeWithDefault(Class<?> clazz)
```
    Return the function type, falling back to the default function type for the provided Class if no function type is explicitly declared. The parameter is necessary because different output classes will have different default function types.
    Examples (For a function with no explicitly declared type):
```
 getTypeWithDefault(String.class); // "interval" function type
 getTypeWithDefault(Number.class); // "exponential" function type
 
```
    Parameters:
    
    clazz - The class for which to return the default function type
    
    Returns:
    
    The function type, falling back to the default when the provided Class is the return type.
    
    See Also:
    
    The "type" header under Mapbox Spec: Functions
  - getProperty
```
public String getProperty()
```
    If specified, the function will take the specified feature property as an input. See Zoom Functions and Property Functions for more information.
    
    Returns:
    
    property evaluated by function, optional (may be null for zoom functions).
  - category
```
public EnumSet<MBFunction.FunctionCategory> category()
```
    Programmatically look at the structure of the function and determine if it is a Zoom function, Property function or Zoom-and-property functions.
    
    Returns:
    
    Classify function as MBFunction.FunctionCategory.PROPERTY, MBFunction.FunctionCategory.ZOOM or both.
  - getStops
```
public JSONArray getStops()
```
    Functions are defined in terms of input and output values. A set of one input value and one output value is known as a "stop."
    
    Returns:
    
    stops definition, optional may be null.
  - getBase
```
public Number getBase()
```
    (Optional) Number. Default is 1. The exponential base of the interpolation curve. It controls the rate at which the function output increases. Higher values make the output increase more towards the high end of the range. With values close to 1 the output increases linearly.
    
    Returns:
    
    The exponential base of the interpolation curve.
  - color
```
public Expression color()
```
    GeoTools Expression from json definition that evaluates to a color, used for properties such as 'color' and 'fill-color'.
    This is the same as numeric() except we can make some assumptions about the values (converting hex to color, looking up color names).
    - MBFunction.FunctionType.IDENTITY: input is directly converted to a color, providing a way to process attribute data into colors.
    - MBFunction.FunctionType.CATEGORICAL: selects stop equal to input value
    - MBFunction.FunctionType.INTERVAL: selects stop less than numeric input value
    - MBFunction.FunctionType.EXPONENTIAL: interpolates an output color between two stops
    If type is unspecified exponential is used as a default.
    Returns:
    
    Function (or identity Expression for the provided json)
  - font
```
public Expression font()
```
    GeoTools Expression from json definition that evaluates to a font string, used for 'text-font'.
    Fonts only use interval functions
    - MBFunction.FunctionType.INTERVAL: selects stop less than numeric input, and returns stop value as a number
    Returns:
    
    Expression providing font string (used for `text-font`)
  - numeric
```
public Expression numeric()
```
    GeoTools Expression from json definition that evaluates to a numeric, used for properties such as 'line-width' and 'opacity'.
    This is the same as color() except we can make some assumptions about the values (converting "50%" to 0.5).
    - MBFunction.FunctionType.IDENTITY: input is directly converted to a numeric output
    - MBFunction.FunctionType.CATEGORICAL: selects stop equal to input, and returns stop value as a number
    - MBFunction.FunctionType.INTERVAL: selects stop less than numeric input, and returns stop value as a number
    - MBFunction.FunctionType.EXPONENTIAL: interpolates a numeric output between two stops
    If type is unspecified exponential is used as a default.
    Returns:
    
    Function (or identity Expression for the provided json)
  - function
```
public Expression function(Class<?> clazz)
```
    GeoTools Expression from json definition.
    Delegates handling of Color, Number and Enum - for generic values (such as String) the following are available:
    - MBFunction.FunctionType.IDENTITY: input is directly converted to a literal
    - MBFunction.FunctionType.CATEGORICAL: selects stop equal to input, and returns stop value as a literal
    - MBFunction.FunctionType.INTERVAL: selects stop less than numeric input, and returns stop value a literal
    If type is unspecified interval is used as a default.
    Parameters:
    
    clazz - Type of data expected
    
    Returns:
    
    Function (or identity Expression for the provided json)
  - enumeration
```
public Expression enumeration(Class<? extends Enum<?>> enumeration)
```
    GeoTools Expression from json definition that evaluates to the provided Enum, used for properties such as 'line-cap' and 'text-transform'.
    - MBFunction.FunctionType.IDENTITY: input is directly converted to an appropriate literal
    - MBFunction.FunctionType.CATEGORICAL: selects stop equal to input, and returns stop value as a literal
    - MBFunction.FunctionType.INTERVAL: selects stop less than numeric input, and returns stop value a literal
    If type is unspecified internval is used as a default.
    Returns:
    
    Function (or identity Expression for the provided json)
  - isArrayFunction
```
public boolean isArrayFunction()
```
    Returns true if this function's stop values are all arrays.
    For example, the following is an array function:
```
 "{'property':'temperature',
   'type':'exponential',
   'base':1.5,
   'stops': [
          // [stopkey, stopValueArray]
             [0,       [0,10]],
             [100,     [2,15]]
    ]
   }"
 
```
    Returns:
    
    true if this function's stop values are all arrays.
  - splitArrayFunction
```
public List<MBFunction> splitArrayFunction()
                                    throws ParseException
```
    Splits an array function into multiple functions, one for each dimension in the function's stop value arrays.
    For example, for the following array function:
```
 "{'property':'temperature',
   'type':'exponential',
   'base':1.5,
   'stops': [
          // [stopkey, stopValueArray]
             [0,       [0,10]],
             [100,     [2,15]]
    ]
   }"
 
```
    This method would split the above function into the following two functions:
    "X" Function:
```
 "{'property':'temperature',
   'type':'exponential',
   'base':1.5,
   'stops': [
          [0,   0],
          [100, 2]
    ]
   }"
 
```
    And "Y" Function:
```
 "{'property':'temperature',
   'type':'exponential',
   'base':1.5,
   'stops': [
          [0,   10],
          [100, 15]
    ]
   }"
 
```
    Returns:
    
    A list of MBFunction, one for each dimension in the stop value array.
    
    Throws:
    
    ParseException

Class MBFunction

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class Object

Field Detail

parse

json

Constructor Detail

MBFunction

MBFunction

Method Detail

getType

getDefault

getTypeWithDefault

getProperty

category

getStops

getBase

color

font

numeric

function

enumeration

isArrayFunction

splitArrayFunction