Control Flow

Conditionals, loops, and pattern matching for dynamic template content.

Raw Blocks

Inside @#...#@ raw blocks (any matching number of #), content is output verbatim - no escaping needed. The @@ escape is only needed outside raw blocks to output a literal @.

Conditionals (@if)

Render content based on conditions:

@if user.is_admin {
    Admin
}

With else

@if user.is_logged_in {
    Welcome back, @user.name!
} else {
    Please sign in.
}

With else if

@if user.role == "admin" {
    Admin
} else if user.role == "moderator" {
    Moderator
} else {
    Member
}

Pattern Matching (if let)

@if let Some(email) = user.email {
    @email
}

@if let Ok(data) = fetch_result {
    @data
} else {
    Failed to load data
}

Conditionals in Attributes

Add attributes conditionally:

Real-world example:


@if let Some(err) = errors.get("email") {
    @err
}

Loops (@for)

Iterate over collections:

@for item in items {
    @item.name
}

With Index

@for (index, item) in items.iter().enumerate() {
    
        @(index + 1)
        @item.name
    
}

With Tuple Destructuring

@for (key, value) in settings {
    @key
    @value
}

Labeled Loops

Use labels with @break and @continue:

@for outer: row in grid.rows {
    
        @for cell in row.cells {
            @if cell.is_stop_marker {
                @break :outer;
            }
            @if cell.is_hidden {
                @continue;
            }
            @cell.value
        }
    
}

Dynamic Attributes in Loops


    Content

Pattern Matching (@match)

Match on enums and values:

@match status {
    Status::Active => {
        Active
    }
    Status::Pending => {
        Pending
    }
    Status::Inactive => {
        Inactive
    }
}

With Destructuring

@match result {
    Ok(user) => {
        Welcome, @user.name!
    }
    Err(e) => {
        Error: @e
    }
}

With Guards

@match score {
    n if n >= 90 => { A }
    n if n >= 80 => { B }
    n if n >= 70 => { C }
    _ => { F }
}

Loop Control

@break

@for item in items {
    @if item.id == target_id {
        Found: @item.name
        @break;
    }
}

@continue

@for item in items {
    @if item.hidden {
        @continue;
    }
    @item.name
}

Complete Example

Combining control flow constructs:

@fn apply(user: Option, items: Vec) {
    @if let Some(user) = user {
        
            Welcome, @user.name!
            @match user.subscription {
                Subscription::Free => {
                    You're on the free plan. Upgrade
                }
                Subscription::Pro => {
                    Pro Member
                }
            }
        

        
            @for (i, item) in items.iter().enumerate() {
                @if !item.archived {
                    
                        @item.name
                        @if let Some(desc) = item.description {
                            @desc
                        }
                    
                }
            }
        
    } else {
        Please sign in to continue.
    }
}