`iviva` Expression Langauge¶

The iviva expression language is a domain-specific mini-language that lets you express logic and formatting instructions in textual form. It provides flexibility to intersperse expressions with regular text. This syntax is used in Template blocks as well as in custom user interfaces to bind data and determine logic.

Syntax¶

All expressions by default are just text. Any special logic, variables and formatting instructions are wrapped in #{....} blocks. Any text outside of those blocks are treated as literal text.

The following is a valid expression:

Good morning, #{auth.Name}!

In this case, the part wrapped in #{...} will be evaluated and the result will be replaced back in the text. The final text output might be:

Good morning, Ricky Ricardo!

In this case, auth is a special object that represents the currently logged-in user and Name is a field of that object that reprsents the user’s full name. See the Available Variables and Objects section for a full list of what variables and objects can be used in expressions.

Logic¶

You can use boolean logic as part of your expression. The following operators are supported:

? - This is the truthy operator. It converts any expression preceding it into a true/false value.

The following values evaluate to false:

empty string

0

null

false

"false" (the text ‘false’)

Other values evaluate to true

and - Example: #{firstvar? and secondvar?} - Returns true if both firstvar and secondvar are true
or - Example: #{firstvar? or secondvar?} - Returns true if any of firstvar and secondvar are true
not - negates the experssion proceding it - Example: #{not firstvar?} - Returns false if firstvar is true

You can use ( and ) to group expressions

Example:

Returns true if either of the values are false

If/else syntax is also supported to evaluate expressions:

#{if firstvar? then secondvar else thirdvar }

This evaluates to secondvar if firstvar is true, else it evalutes to thirdvar

Formatting¶

If you need to include literal text inside an expression, put it inside square brackets:

If the authorized variable is true then evaluate to the text “Ok” else evaluate to the text “Sorry, no access permitted”

Transformers¶

Transformers are special functions that transform an expression in some way. Put a pipe (|) character after an expression and then the name of the transformer to transform that expression.

One such transformer is the datetimeformat transformer. That transforms an expression which evaluated to a timestamp into a nicely formatted textual representation of the timestamp according to the logged-in user’s format preferences.

#{services.details.CreatedDateTime|datetimeformat}

This returns the CreateDateTime value in a nicely formatted text.

Functions¶

There are several predefined functions that can be used within expressions. The syntax for functions is:

Functions can be nested.

Available Variables and Objects¶

param¶

Use this object to read page input values.

Example: .. code:

#{if param.enable? then [Ok] else [No]}

Checks if enable is passed as a query string parameter and is set to some value except 0 or empty and then returns “OK” or “No” accordingly.

services¶

Use this to read data from any datasources defined in a UI bundle. To read a field from a datasource, the syntax is #{sevices.datasource.field}

All the data in a source can be returned as serialized JSON by using:

#{services.datasource.__rawdata__|json}

This returns a JSON representation of a data source. This is useful if you want to process a datasource entirely in javascript on a page.

authrole¶

Use this to check if the logged-in user has a specified |approle|

Syntax: #{authrole.app.rolename?}

Where app is the application name and rolename is the name of the role to check

Returns true if the current user has the specified app role.

For checking model roles, use #{authrole.Lucy.model.modelname.rolename?}

baseurl¶

This variable returns the relative root of the iviva application. Use this to construct a relative path for a url within iviva

Example: .. code:

#{baseurl}/Apps/Lucy/dashboard

fullaccounturl¶

The full path to the root of the iviva application. Use this to construct absolute paths for a url within iviva Example: .. code:

#{baseurl}/Apps/Lucy/dashboard

auth¶

Use this object to access details about the logged-in user. The syntax is #{auth.FieldName}

Where FieldName can be any of the following:

Name - the user’s full name
LoginID - the user’s login id
UserKey - the iviva user key associated with this user.

Available Transformers¶

int¶

convert to an integer

str¶

convert to a string

exists¶

check if the value is null or empty

validint¶

check if the value is a non-zero integer

float¶

convert to a floating point value

floatstr(precision)¶

converts to a formatted string with given precision (from 1 - 7) Example:

clip(length)¶

clip to a specified length and add ellipsis at the end

trim¶

Trim out the leading and trailing space of strings

duration¶

Converts an integer (in minutes) into a user friendly duration Example: .. code:

#{row.TotalMinutes|duration} - returns ‘10min’ or ‘1hr 30min’ or ‘2 days’ etc...

capitalize¶

Capitalizes the first character of the specified text

dateformat¶

Convert the date value into text formatted in the user’s preferred date format

minutesago¶

return how many minutes have passed since the datetime value specified

datetimeformat¶

Converts the datetime into text using the user’s preferred datetime format and in the user’s timezone

timeformat¶

Converts the time into text using the user’s preferred time format

Available Functions¶

concat(str1,str2,…)¶

combines multiple strings together Example:

sum(i1,i2...)¶

sum of multiple integers

mod(i1,i2)¶

i1 % i2

mul(i1,i2,…)¶

multiply multiple integers

fmul(f1,f2,…)¶

multiply multiple floating point values

random(start,end)¶

returns a random number between start and end

randomchoice(item1,item2,…)¶

returns one of the specified items at random Example:

startswith(a,b)¶

returns true if b is a prefix of a (case insensitive)

substring(a,i1)¶

return a substring of ‘a’ starting at i1 (zero-based index)

substring(a,i1,i2)¶

return a substring of ‘a’ starting at i1 and i2 characters long

len(a)¶

length of the string specified in ‘a’

iviva Expression Langauge¶