mx-space / zod-patterns

Skill Content

---
name: zod-patterns
description: MX Space project Zod schema patterns. Apply when creating DTOs, validation schemas, or handling request validation.
user-invocable: false
---

# Zod Schema Patterns

## Basic Pattern

```typescript
import { z } from 'zod'
import { createZodDto } from 'nestjs-zod'

// Define Schema
export const MySchema = z.object({
  name: z.string().min(1),
  email: z.string().email(),
  age: z.number().int().positive().optional(),
})

// Create DTO class
export class MyDto extends createZodDto(MySchema) {}

// Partial DTO for updates
export class PartialMyDto extends createZodDto(MySchema.partial()) {}
```

## Project Custom Validators

Location: `apps/core/src/shared/schema/base.schema.ts`

```typescript
import {
  zMongoId,           // MongoDB ObjectId validation
  zNonEmptyString,    // Non-empty string
  zArrayUnique,       // Unique array elements
  zPinDate,           // Pin date validation
} from '~/shared/schema/base.schema'

const Schema = z.object({
  id: zMongoId,
  title: zNonEmptyString,
  tags: zArrayUnique(z.string()),
  pin: zPinDate,
})
```

## Extending Base Schemas

```typescript
import { WriteBaseSchema } from '~/shared/schema/write-base.schema'
import { ImageSchema } from '~/shared/schema/image.schema'

// Extend WriteBaseSchema (includes title, text, images, etc.)
export const PostSchema = WriteBaseSchema.extend({
  slug: zNonEmptyString,
  categoryId: zMongoId,
  tags: zArrayUnique(z.string()).optional(),
})
```

## Common Patterns

### Optional Fields with Defaults

```typescript
z.boolean().default(true).optional()
z.number().default(0).optional()
z.array(z.string()).default([]).optional()
```

### Preprocessing

```typescript
// Empty string to null
z.preprocess(
  (val) => (val === '' ? null : val),
  z.string().nullable()
).optional()

// String to number
z.preprocess(
  (val) => (typeof val === 'string' ? parseInt(val, 10) : val),
  z.number()
)
```

### Union Types

```typescript
z.union([z.string(), z.number()])
z.enum(['draft', 'published', 'archived'])
```

### Array Validation

```typescript
// Basic array
z.array(z.string())

// Length constraints
z.array(z.string()).min(1).max(10)

// Unique elements
zArrayUnique(z.string())
```

### Nested Objects

```typescript
const AddressSchema = z.object({
  street: z.string(),
  city: z.string(),
})

const UserSchema = z.object({
  name: z.string(),
  address: AddressSchema.optional(),
  addresses: z.array(AddressSchema).optional(),
})
```

### Conditional Validation

```typescript
// refine for custom validation
z.object({
  password: z.string(),
  confirmPassword: z.string(),
}).refine(
  (data) => data.password === data.confirmPassword,
  { message: 'Passwords must match' }
)
```

## Mapping to TypeGoose Models

```typescript
// Model
export class PostModel extends WriteBaseModel {
  @prop({ required: true })
  slug!: string

  @prop({ type: () => [String] })
  tags?: string[]
}

// Schema
export const PostSchema = WriteBaseSchema.extend({
  slug: zNonEmptyString,           // Maps to required
  tags: z.array(z.string()).optional(), // Maps to optional field
})
```

## Type Inference

```typescript
// Infer type from Schema
type MyType = z.infer<typeof MySchema>

// Use in Service
async create(data: z.infer<typeof MySchema>) {
  return this.model.create(data)
}
```