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Expressions

The expression engine allows you to add dynamic logic to templates. Use expressions for text interpolation, conditional rendering, and data transformation.

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Syntax

Expressions use double curly braces: {{expression}}

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Simple Variables

{{title}}
{{user.name}}
{{items[0].price}}

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Property Access

Access nested properties with dot notation: 
{{user.profile.avatar}}
{{order.items[0].name}}

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Arithmetic

{{price * quantity}}
{{subtotal + tax}}
{{total / 100}}
{{count % 2}}

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Comparisons

{{price > 100}}
{{status == 'active'}}
{{count >= 10}}
{{name != 'Guest'}}

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Logical Operators

{{isAdmin && isPremium}}
{{hasDiscount || isFirstOrder}}
{{!isExpired}}

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Ternary Operator

{{isPremium ? 'Premium Member' : 'Free User'}}
{{count > 0 ? count : 'None'}}

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Built-in Functions

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String Functions

FunctionDescriptionExample
uppercase(str)Convert to uppercase{{uppercase(name)}}
lowercase(str)Convert to lowercase{{lowercase(email)}}
capitalize(str)Capitalize first letter{{capitalize(title)}}
titleCase(str)Capitalize each word{{titleCase(name)}}
trim(str)Remove whitespace{{trim(input)}}
truncate(str, len, suffix)Truncate with suffix{{truncate(desc, 100, '...')}}
replace(str, search, replace)Replace all occurrences{{replace(text, '-', ' ')}}
split(str, delimiter)Split into array{{split(tags, ',')}}
padStart(str, len, char)Pad from start{{padStart(id, 5, '0')}}
padEnd(str, len, char)Pad from end{{padEnd(code, 10, '-')}}

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Number Functions

FunctionDescriptionExample
round(num, decimals)Round to decimals{{round(price, 2)}}
floor(num)Round down{{floor(rating)}}
ceil(num)Round up{{ceil(shipping)}}
abs(num)Absolute value{{abs(difference)}}
min(a, b, ...)Minimum value{{min(price, maxPrice)}}
max(a, b, ...)Maximum value{{max(0, quantity)}}
sum(array)Sum array values{{sum(prices)}}
average(array)Average of array{{average(ratings)}}

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Formatting Functions

FunctionDescriptionExample
currency(num, currency, locale)Format as currency{{currency(price, 'USD')}}
number(num, locale)Format number{{number(count, 'en-US')}}
percent(num, decimals)Format as percent{{percent(rate, 1)}}
date(str, format)Format date{{date(createdAt, 'MMM D, YYYY')}}
time(str)Format time{{time(timestamp)}}

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Array Functions

FunctionDescriptionExample
length(arr)Array length{{length(items)}}
first(arr)First element{{first(images)}}
last(arr)Last element{{last(comments)}}
join(arr, separator)Join elements{{join(tags, ', ')}}
slice(arr, start, end)Slice array{{slice(items, 0, 3)}}
contains(arr, value)Check if contains{{contains(roles, 'admin')}}
indexOf(arr, value)Find index{{indexOf(items, 'apple')}}

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Type Checks

FunctionDescriptionExample
isEmpty(val)Check if empty{{isEmpty(items)}}
isNotEmpty(val)Check if not empty{{isNotEmpty(name)}}
isDefined(val)Check if defined{{isDefined(user)}}
isArray(val)Check if array{{isArray(items)}}
isString(val)Check if string{{isString(name)}}
isNumber(val)Check if number{{isNumber(count)}}

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Utilities

FunctionDescriptionExample
default(val, fallback)Default if empty{{default(name, 'Guest')}}
coalesce(a, b, ...)First non-null{{coalesce(nickname, name, 'User')}}
json(val)To JSON string{{json(data)}}
parseJson(str)Parse JSON{{parseJson(jsonString)}}

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Conditional Rendering

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If/Else in Text

{{isPremium ? 'Premium Member' : 'Free User'}}

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Conditional Objects

In template objects, use the _if property: 
{
  "type": "textbox",
  "text": "Premium Badge",
  "_if": "isPremium"
}
The object is only rendered if the condition evaluates to true.

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Complex Conditions

{
  "type": "image",
  "src": "{{badge}}",
  "_if": "isPremium && !isExpired"
}

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Text Interpolation

Combine static text with expressions: 
Hello, {{name}}! You have {{count}} {{count == 1 ? 'message' : 'messages'}}.
Multiple expressions in one string: 
{{currency(price, 'USD')}} ({{percent(discount)}} off)

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Testing Expressions

Test expressions before using them in templates:

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Validate Syntax

curl -X POST https://api.pictify.io/templates/expression/validate \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"expression": "price * quantity"}'
Response: 
{
  "valid": true,
  "expression": "price * quantity"
}

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Test with Data

curl -X POST https://api.pictify.io/templates/expression/test \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "expression": "currency(price * quantity, 'USD')",
    "variables": {
      "price": 29.99,
      "quantity": 3
    }
  }'
Response: 
{
  "success": true,
  "result": "$89.97",
  "resultType": "string"
}

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List Available Functions

curl https://api.pictify.io/templates/expression/functions \
  -H "Authorization: Bearer $API_KEY"

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Examples

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Personalized Greeting

{{capitalize(greeting)}}, {{titleCase(name)}}!

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Price Display

{{currency(price, 'USD')}}{{hasDiscount ? ' (' + percent(discount) + ' off)' : ''}}

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Date Formatting

Published {{date(publishedAt, 'MMMM D, YYYY')}}

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Conditional Badge

{
  "type": "rect",
  "fill": "{{isPremium ? '#FFD700' : '#C0C0C0'}}",
  "_if": "showBadge"
}

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Array Display

{{join(slice(tags, 0, 3), ' • ')}}{{length(tags) > 3 ? ' +' + (length(tags) - 3) + ' more' : ''}}