A function is a piece of dart code that performs a specific task.
So a function can basically do anything that dart code can do.
A function can be used anywhere in an tag expression. Wherever that particular task should be performed.
An example of a function call: cos(pi)
Should result in: -1
Function & Parameter & argument names:
are case sensitive
must start with a lower case letter, optionally followed by (lower or upper case) letters and or digits.
conventions: use lowerCamelCase
must be unique and does not match a other tag syntax
Parameters vs Arguments
Parameters are the names used in the function definition.
Arguments are the actual values passed when calling the function.
Parameters:
A function can have zero or more parameters
Parameters are defined as either mandatory or optional
Optional parameters can have a default value
Arguments:
Multiple arguments are separated with a comma, e.g. single argument: cos(pi) multiple arguments: volume(10,20,30)
There are different types of arguments
Positional Arguments: These are passed in the order the function defines them. e.g.: volume(10, 20, 30)
Named Arguments: You can specify which parameter you're assigning a value to, regardless of order. e.g.: volume(l=30, h=10, w=20)
Arguments can set a parameter only once
You can mix positional arguments and named arguments, but positional arguments must come first
Named arguments remove ambiguity: If you want to skip an optional argument or specify one out of order, you must name it explicitly
Argument values:
must match the expected parameter type. e.g. area(length='hello', width='world') will result in a failure
may be a tag expression such as a variable, constant, operation, function, or combination. e.g. cos(2*pi)
You can use prepackaged [template_engine] functions or add your own custom functions by manipulating the TemplateEngine.functionGroups field.Example .
description:
Returns the natural exponent e, to the power of the value
return type:
number
expression example:
{{exp(7)}} should render: 1096.6331584284585
code example:
exp_test.dart
parameter:
value
number
mandatory
description:
Returns the natural logarithm of the value
return type:
number
expression example:
{{log(7)}} should render: 1.9459101490553132
code example:
log_test.dart
parameter:
value
number
mandatory
description:
Returns the sine of the radians
return type:
number
expression example:
{{sin(7)}} should render: 0.6569865987187891
code example:
sin_test.dart
parameter:
radians
number
mandatory
description:
Returns the values arc sine in radians
return type:
number
expression example:
{{asin(0.5)}} should render: 0.5235987755982989
code example:
asin_test.dart
parameter:
value
number
mandatory
description:
Returns the cosine of the radians
return type:
number
expression example:
{{cos(7)}} should render: 0.7539022543433046
code example:
cos_test.dart
parameter:
radians
number
mandatory
description:
Returns the values arc cosine in radians
return type:
number
expression example:
{{acos(0.5)}} should render: 1.0471975511965979
code example:
acos_test.dart
parameter:
value
number
mandatory
description:
Returns the the tangent of the radians
return type:
number
expression example:
{{tan(7)}} should render: 0.8714479827243188
code example:
tan_test.dart
parameter:
radians
number
mandatory
description:
Returns the values arc tangent in radians
return type:
number
expression example:
{{atan(0.5)}} should render: 0.4636476090008061
code example:
atan_test.dart
parameter:
value
number
mandatory
description:
Returns the positive square root of the value.
return type:
number
expression example:
{{sqrt(9)}} should render: 3.0
code example:
sqrt_test.dart
parameter:
value
number
mandatory
description:
Returns the a rounded number.
return type:
number
expression example:
{{round(4.445)}} should render: 4
code example:
round_test.dart
parameter:
value
number
mandatory
description:
Returns the length of a string
return type:
number
expression example:
{{length("Hello")}} should render: 5
code example:
length_test.dart
parameter:
string
String
mandatory
tagDocumentation Function
description:
Generates markdown documentation of all the tags within a TemplateEngine
return type:
String
expression example:
{{ tagDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
dataTypeDocumentation Function
description:
Generates markdown documentation of all the data types that can be used within a ExpressionTag of a TemplateEngine
return type:
String
expression example:
{{ dataTypeDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
constantDocumentation Function
description:
Generates markdown documentation of all the constants that can be used within a ExpressionTag of a TemplateEngine
return type:
String
expression example:
{{ constantDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
variableDocumentation Function
description:
Generates markdown documentation of variables that can be used within a ExpressionTag of a TemplateEngine
return type:
String
expression example:
{{ variableDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
functionDocumentation Function
description:
Generates markdown documentation of all the functions that can be used within a ExpressionTag of a TemplateEngine
return type:
String
expression example:
{{ functionDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
operatorDocumentation Function
description:
Generates markdown documentation of all the operators that can be used within a ExpressionTag of a TemplateEngine
return type:
String
expression example:
{{ operatorDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
exampleDocumentation Function
description:
Generates markdown documentation of all the examples. This could be used to generate example.md file.
return type:
String
expression example:
{{ exampleDocumentation() }}
parameter:
titleLevel
number
optional (default=1)
The level of the tag title
description:
Gives the relative path of the current template
return type:
String
expression example:
{{templateSource()}}
code example:
template_test.dart
description:
Imports, parses and renders a template file
return type:
IntermediateRenderResult
expression example:
{{importTemplate('test/src/parser/tag/expression/function/import/to_import.md.template')}}
code example:
import_template_test.dart
parameter:
source
String
mandatory
The project path of the template file
description:
Imports a file as is (without parsing and rendering)
return type:
String
expression example:
{{importPure('test/src/template_engine_template_example_test.dart')}}
code example:
import_pure_test.dart
parameter:
source
String
mandatory
The project path of the file. This path can be a absolute or relative file path or URI.
description:
Imports a JSON file and decode it to a Map, which could be assigned it to a variable.
return type:
Map
expression example:
{{json=importJson('test/src/parser/tag/expression/function/import/person.json')}}{{json.person.child.name}}
code example:
import_json_test.dart
parameter:
source
String
mandatory
The project path of the JSON file. This path can be a absolute or relative file path or URI.
description:
Imports a XML file and decode it to a Map, which could be assigned it to a variable.
return type:
Map
expression example:
{{xml=importXml('test/src/parser/tag/expression/function/import/person.xml')}}{{xml.person.child.name}}
code example:
import_xml_test.dart
parameter:
source
String
mandatory
The project path of the XML file. This path can be a absolute or relative file path or URI.
description:
Imports a YAML file and decode it to a Map, which could be assigned it to a variable.
return type:
Map
expression example:
{{yaml=importYaml('test/src/parser/tag/expression/function/import/person.yaml')}}{{yaml.person.child.name}}
code example:
import_yaml_test.dart
parameter:
source
String
mandatory
The project path of the YAML file. This path can be a absolute or relative file path or URI.