Declaring Data Objects and Types

Built-in Types

See Flex Syntax Overview

Constants (const)

A constant object of a data type may be declared using the const keyword.

Syntax

const NAME : TYPE = VALUE;

Example

Declare a constant object of the float64 data type named pi:

flex
const pi : float64 = 3.14159265359;

Declare a constant object of an array of the uint8 data type named uuid:

flex
const uuid : uint8[] = [0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0];

Declare a constant object of a user-defined struct space3D data type named coord:

flex
const coord : space3D = space3D {x = 1.2; y = -2.0; z = 6.0;};

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Structured Types (struct)

A structured type object may be declared using the struct keyword.

Zero or more fields may be declared within a struct, and each field must have a data type declared after its name. Properties may be declared after field declarations.

Syntax

struct NAME { FIELDS ; PROPERTIES }

Example

Declare a struct with fields of the float64 type named space3D:

flex
struct space3D {
    x : float64;
    y : float64;
    z : float64;
}

Declare a struct with fields of Optional types named Result:

flex
struct Result {
    num : Optional<int32>;
    str : Optional<string>;
}

Struct Properties

Structs may include field assertions after field declarations. Field assertions are declared using the assert keyword.

Example

Declare a struct named GreaterThan100 with a field named count that must be greater than 100:

flex
struct GreaterThan100 {
    count : int32;
    assert count > 100;
}

Extending Structs

A struct can extend an existing one using the extends keyword. The new struct will contain the fields from the existing struct plus the new ones declared.

To make a struct extensible, it must be declared using the extensible struct keyword.

Example

Declare an extensible struct named Base, then declare a struct named BaseExtended that extends it:

flex
extensible struct Base {
    ID : uint8;
    Name : string;
}
struct BaseExtended extends Base {
    Time : float64;
}

BaseExtended will contain the fields ID, Name, and Time.

---

Enumerated Types (enum)

An enumerated type object may be declared using the enum keyword.

Its data type must be declared after its name, and all the values within it must be of that data type.

Syntax

enum NAME TYPE { FIELD VALUE PAIRS }

Example

Declare an enum named SimulationStatusType with values of the int32 type:

flex
enum SimulationStatusType int32 {
  Stopped = 0;
  Running = 1;
  Paused = 2;
  Reset = 3;
}

---

Variant Types (variant)

A variant type object may be declared using the variant keyword.

Variants are useful when handling different result types. For example, if you need the result of a function to either be of type string or float32, then a variant can facilitate that.

Syntax

variant NAME { FIELDS }

Example

Declare a variant named Result with two possible types, either string or float32:

flex
variant Result {
    Error(string);
    Value(float32);
}

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Message Types (message)

Messages are a special type of object that you can use in Tangram Pro^TM when designing component software interfaces. They may be used for the parameters or return value of transform functions. A message type object may either be a struct or a variant.

Message Structs

A message struct type object may be declared using the message struct keyword. They are similar to Structured Types.

Syntax

message struct NAME { FIELDS ; PROPERTIES }

Example

Declare a message struct named Route which utilizes a struct named Location:

flex
struct Location {
    Latitude : float64;
    Longitude : float64;
    Altitude : float32;
}
message struct Route {
    RouteID : int64;
    Start : Location;
    Stop : Location;
}

Message Struct Properties

Message structs may include field assertions after field declarations. See Struct Properties.

Extending Message Structs

Message structs can be extended. See Extending Structs.

Message Variants

A message variant type object may be declared using the message variant keyword. They are similar to Variant Types.

Syntax

message variant NAME { FIELDS }

Example

Declare a message variant named Result:

flex
message variant Result {
    Error(string);
    Value(float32);
}

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New Types (newtype)

A new type object may be declared using the newtype keyword.

New types must have one field declared within it, along with its data type. Properties may be declared after the field declaration.

New types may be used for the parameters or return value of transform functions.

Syntax

newtype NAME {FIELD ; PROPERTIES}

Example

Declare two newtype objects named MPH and KMPH which both utilize a struct field Velocity.speed:

flex
struct Velocity {
    speed : float64;
    angle : float64;
}
newtype MPH {
    value : Velocity.speed;
}
newtype KMPH {
    value : Velocity.speed;
}

New Type Properties

Similar to structs, new types may include field assertions after the field declaration. See Struct Properties.

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Accessing Fields

Object fields are accessed using the dot syntax.

Syntax

OBJECT.FIELD

Example

Given a struct named space3D, and a const of it named coord:

flex
struct space3D {
    x : float64;
    y : float64;
    z : float64;
}
const coord : space3D = space3D {x = 1.2; y = -2.0; z = 6.0;}; 

Access the field x:

flex
coord.x