Vapor 大型教程
数据库迁移
随着功能迭代，数据表结构也得跟着变。本文用 Vapor 3 的 Fluent 迁移，给 User 加 Twitter 字段、给 Category 加唯一约束，并按环境创建管理员账号。
一、给用户加一个 Twitter 账号显示
先在 User 模型上增加一个可选的 twitterURL 字段，并同步更新公开结构体与迁移：
...
final class User: Codable {
...
var twitterURL: String?
init(name: String, username: String, password: String, twitterURL: String? = nil) {
...
self.twitterURL = twitterURL
}
final class Public: Codable {
...
var twitterURL: String?
init(id: UUID?, name: String, username: String, twitterURL: String? = nil) {
...
self.twitterURL = twitterURL
}
}
}
...
extension User {
func convertToPublic() -> User.Public {
return User.Public(id: self.id, name: self.name, username: self.username, twitterURL: self.twitterURL)
}
}
...
extension User: Migration {
static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
return Database.create(self, on: conn, closure: { (builder) in
builder.field(for: \.id, isIdentifier: true)
builder.field(for: \.name)
builder.field(for: \.username)
builder.field(for: \.password)
builder.unique(on: \.username)
})
}
}但已上线的数据库不会自动加字段，需要新建一个迁移来改表。新建文件 18-12-26-AddTwitterToUser.swift：
import FluentPostgreSQL
import Vapor
struct AddTwitterURLToUser: Migration {
typealias Database = PostgreSQLDatabase
static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
return Database.update(User.self, on: conn) { builder in
builder.field(for: \.twitterURL)
}
}
static func revert(on conn: PostgreSQLConnection) -> Future<Void> {
return Database.update(User.self, on: conn) { builder in
builder.deleteField(for: \.twitterURL)
}
}
}在 configure.swift 里注册这个迁移：
public func configure(_ config: inout Config, _ env: inout Environment, _ services: inout Services) throws {
...
migrations.add(migration: AddTwitterURLToUser.self, database: .psql)
services.register(migrations)
...
}然后在 Web 端把 Twitter 字段展示出来。注册表单加上 Twitter 输入框：
...
<form method="post">
<div class="form-group">
<label for="name">Name</label>
<input type="text" name="name" class="form-control"
id="name"/>
</div>
<div class="form-group">
<label for="twitterURL">Twitter handle</lable>
<input type="text" name="twitterURL" class="form-control" id="twitterURL" />
</div>
...用户详情页 user.leaf 显示它：
<h1>#(user.name)</h1>
<h2>#(user.username)
#if(user.twitterURL) {
- #(user.twitterURL)
}
</h2>
...注册处理逻辑读取这个字段（为空则存 nil）：
...
struct RegisterData: Content {
...
let twitterURL: String?
}
...
func registerPostHandler(_ req: Request, data: RegisterData) throws -> Future<Response> {
...
var twitterURL: String?
if let twitter = data.twitterURL, !twitter.isEmpty {
twitterURL = twitter
}
let user = User(name: data.name, username: data.username, password: password, twitterURL: twitterURL)
...
}
...二、让类别具有唯一性
类别名应该唯一，避免重复创建同名类别。新建迁移 18-12-26-MakeCategoriesUnique.swift，给 name 加唯一约束，并能在回滚时删除它：
import FluentPostgreSQL
import Vapor
struct MakeCategoriesUnique: Migration {
typealias Database = PostgreSQLDatabase
static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
return Database.update(Category.self, on: conn) {
builder in
builder.unique(on: \.name)
}
}
static func revert(on conn: PostgreSQLConnection) -> Future<Void> {
return Database.update(Category.self, on: conn) { builder in
builder.deleteUnique(from: \.name)
}
}
}同样在 configure.swift 注册：
public func configure(_ config: inout Config, _ env: inout Environment, _ services: inout Services) throws {
...
migrations.add(migration: MakeCategoriesUnique.self, database: .psql)
services.register(migrations)
...
}三、只在开发和测试环境上创建管理员账号
管理员账号不该出现在生产库里。借助 env 判断，只在开发/测试环境注册创建管理员的迁移：
public func configure(_ config: inout Config, _ env: inout Environment, _ services: inout Services) throws {
...
switch env {
case .development, .testing:
migrations.add(migration: AdminUser.self, database: .psql)
default:
break
}
migrations.add(migration: AddTwitterURLToUser.self, database: .psql)
migrations.add(migration: MakeCategoriesUnique.self, database: .psql)
services.register(migrations)
...
}迁移的本质：每个迁移都有
prepare 和 revert 两个方法，revert 负责把改动撤销回去。给迁移文件加上日期前缀（如 18-12-26-）是个好习惯，方便排序和追溯。