Transforms & Hooks

Meerkat provides built-in attributes for automatic string transformations and lifecycle methods for custom business logic before and after document persistence.

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Data Transformations

Apply [Lowercase] or [Uppercase] attributes to model string properties to transform their values automatically before each document save.

using meerkat;
using meerkat.Attributes;

public class User : Schema<Guid>
{
    [Lowercase]
    public string Email { get; set; } = string.Empty;

    [Uppercase]
    public string CountryCode { get; set; } = string.Empty;
}

Constraints & Validation

• Both attributes are strictly restricted to properties of type string.
• Applying [Lowercase] or [Uppercase] to non-string properties throws an InvalidAttributeException at runtime when inspected.
• Null string values are safely ignored and remain null.

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Lifecycle Hooks

Override the PreSave and PostSave virtual methods on any model inheriting from Schema<TId> to run custom logic during document persistence:

using meerkat;
using MongoDB.Bson;

public class Student : Schema<ObjectId>
{
    public string FirstName { get; set; } = string.Empty;
    public string LastName { get; set; } = string.Empty;

    public override void PreSave()
    {
        // Executes after timestamp generation and case transformations,
        // right before the document is written to MongoDB.
        FirstName = FirstName?.Trim() ?? string.Empty;
        LastName = LastName?.Trim() ?? string.Empty;
    }

    public override void PostSave()
    {
        // Executes immediately after the MongoDB ReplaceOne write completes.
    }
}

Execution Order during Save

When calling Save() or SaveAsync() (and in bulk SaveAll() / SaveAllAsync()):

1. Timestamps: Sets CreatedAt (if first save) and UpdatedAt (if TrackTimestamps = true).
2. Transforms: Evaluates [Lowercase] and [Uppercase] attributes on string properties.
3. PreSave: Calls the model's PreSave() method.
4. Database Write: Executes ReplaceOne with upsert enabled on MongoDB.
5. PostSave: Calls the model's PostSave() method.

Write-Path Difference

Partial updates (via Update<TSchema, TId>(), UpdateOne, UpdateMany, UpdateByFilter, or atomic increment/decrement helpers) do not invoke PreSave(), PostSave(), or data transformations because documents are modified directly at the field level within MongoDB.