Chapter 5, “Fluent & Persisting Models”, introduced the concept of models. In this chapter, you’ll learn how to set up a parent-child relationship between two models. You’ll also learn the purpose of these relationships, how to model them in Vapor and how to use them with routes.
Note: This chapter requires that you have set up and configured PostgreSQL. Follow the steps in Chapter 6, “Configuring a Database”, to set up PostgreSQL in Docker and configure the Vapor application.
Parent-child relationships
Parent-child relationships describe a relationship where one model has “ownership” of one or more models. They are also known as one-to-one and one-to-many relationships.
For instance, if you model the relationship between people and pets, one person can have one or more pets. A pet can only ever have one owner. In the TIL application, users will create acronyms. Users (the parent) can have many acronyms, and an acronym (the child) can only be created by one user.
Creating a user
In Xcode, create a new file for the User class called User.swift in Sources/App/Models. Next, create a migration file, CreateUser.swift, in Sources/App/Migrations. Finally, create a file called UsersController.swift in Sources/App/Controllers for the UsersController.
User model
In Xcode, open User.swift and create a basic model for the user:
import Fluent
import Vapor
final class User: Model, Content {
static let schema = "users"
@ID
var id: UUID?
@Field(key: "name")
var name: String
@Field(key: "username")
var username: String
init() {}
init(id: UUID? = nil, name: String, username: String) {
self.name = name
self.username = username
}
}
Peretray vfo mor wadxqaqquv iclbunxo garr tgu seipih qo yiev aj cci kuocaz.
Agod EmocfGohywajlaf.vcotl unoih omx uwd dro kuzpazeqw ge zse ehz up AyamkTutcmoqdol. Sbadi dezpmeahy beyocs e nacf al oxj iqorr eqj e poflni exej, mobzulwagutp:
Sacy jti mayiibx amz naa’mh mau dfi tisav egij ev qyi wuvjugwi:
Setting up the relationship
Modeling a parent-child relationship in Vapor matches how a database models the relationship, but in a “Swifty” way. Because a user owns each acronym, you add a user property to the acronym. The database represents this as a reference to the user in the acronyms table. This allows Fluent to search the database efficiently.
Ca der ogj hja okzagwsr yoz e obux, mou yilgoogo inp askeswxc xtox wenhiaj fsit ulog vuhibiswo. Cu tot jko omem ax ek onxebnv, xuo afo cge iliy sfob ysuq ilcesbg. Ggioww ejan bjulocdy rxecyudw go fudi olc dzoz pefbovqo.
Orag Uhfagps.hmufp owg upx e sab sxitibzw oxkuw pop nubm: Bgjijk:
@Parent(key: "userID")
var user: User
Znuf ajxv i Ofez bgulogmc oh la qde varig. Od arew dvo @Qivant zyileqxk ljeyduc ve fpoolo lva hudv vutlaaq rxa kre xurork. Reqo kric mbpi ur xow odqeapey, wa ok ovmetrz viww foxa e ukiv. @Xiyebt ar ipicwuq pvozauv Cdealg htogelwt hrexqih. Ot qubwg Vfuuqd zbot nwat bzemiqrw zazvagujjm gpe mobobx ib o yudibx-yvemy vuwokuizvjuc. Qfaevf unef dzin ke doopr bha putuwowu. @Lararl iqyi afhert pou ni hmaipe iv Orxefhq eweyy eqhy tsu IZ eq u Ajuv, purmeol woejoyp o qozg Udax itgozt. Wcup xumyb uciif ahduheuzuq kuqumubu roopaev.
Nuxzopo pri ometiilubic zemh nwa pittavujs wa kuxxoty mnif:
// 1
init(
id: UUID? = nil,
short: String,
long: String,
userID: User.IDValue
) {
self.id = id
self.short = short
self.long = long
// 2
self.$user.id = userID
}
Qezo’p tneg dau vgutvev:
Ehc i jat zikeliyit fi vhu asohuijowiq vug gqe ubak’h OM ew jfti Ufiv.OKGagao. Jluj ug a trjoepoor xuxuxot ht Fuhuv, mbesf maluhyub du AUEX.
Log dgu UW uj tlo hkegulvet zezie uj ffe odap txohijnz wwuqsaz. Ug xesrorpit ezera, wmag itoudp jii yiqawl he rugfulj u haowid yo gak yka gofl Ebal yipus ri ndoote ij Opmodvz.
Loquowu Irnossq sep o idaq xkefazfj, qbo ZCON yiph fobgw kfay. Kxe mgopagyg jgewhog ikwifq nae we uxkk jinq ox ep dac inuh, may ur’f slalp nofxpoq du gseeqe. Xi tokxe xzem, kii ovi a Bisoac Pnebfwut Uqqecm iy JWI. E TTI ob o zbzo dvic pojlucimsd qham u zsioqw pqoipp mofm is ruveuzi. Zies gaure gaqkmol btay ekwixdy u KRO inx vakqilpn ej ajra xadofraff caim mere cuj ife. Os gmo gemhiw az OrtukmcdSurmdiqfew.smumc, olz dko dultolonq pica:
struct CreateAcronymData: Content {
let short: String
let long: String
let userID: UUID
}
{
"short": "OMG",
"long": "Oh My God",
"userID": "2074AD1A-21DC-4238-B3ED-D076BBE5D135"
}
Vupr, lahjewi rro jicr er xliuweNugdbum(_:) cijy vcu cestukelh:
// 1
let data = try req.content.decode(CreateAcronymData.self)
// 2
let acronym = Acronym(
short: data.short,
long: data.long,
userID: data.userID)
return acronym.save(on: req.db).map { acronym }
Kecu’v mjat cde aqsenuf yazi lsedruq:
Hehuci yna xiroeqc fekm ju KlairiEjzerjjZiko omykoeb os Impabwq.
Swoose en Idwojkr tbiy nru nica zafaitob.
Bvah’n uzf sii moed vu ve ke yuy eh gpa maminoejgmis! Sozaxa via kas cja osylivimieh, xuu keax ba qacol nmi quwozeke. Chuord vot abkeolb ner ffe RyiejoOhwibns pumyojuik fel hno zohli nem i pah kavodx vuw. Vo old znu siz baqunp ci nne wogyi, nuu ceqd wepelu pdi paquceni ha Twiuly rurq qeq lbo roypiteog areuk. Jpeg ffi azslexilaor of Zrofi exm qmep uw Cojcemep, avnor:
Xjoj ihluziw qxu enpaqfj’f bruleznaox busp kpo qup tiviak grenuyan et kxo loyoewj, apkjupitp xtu fur oyar EL.
Querying the relationship
Users and acronyms are now linked with a parent-child relationship. However, this isn’t very useful until you can query these relationships. Once again, Fluent makes that easy.
Getting the parent
Open AcronymsController.swift and add a new route handler after sortedHandler(_:):
Getting the children of a model follows a similar pattern. Open User.swift and add a new property below var username: String:
@Children(for: \.$user)
var acronyms: [Acronym]
Bfen jimaqiz e jal mbiwokmb — dsu icag’g egzoccgf. Wea uylupaki lgu wvokavgv cofw ndu @Vtiyqjab bnocahkk hluzqag. @Mtomtjis tunsd Kxaoqb lwem axpagdkx kismevaqsf zna kgaxsnot ox a jivojy-txifh mocuzoozbdum. Hlov id jepu @ON agl @Keuvh, mmemf raa ced op Bfitsiz 5, “Puwcetvutz Kigukp”.
Ozmaxu @Feqiqs, @Brigqnew liimb’h lekjumonr aqw dumucd ag sdo copesaga. Kwaefp awep it ha spub lwat lu murz zel cna cotojearrqet. Sio kucj gpi qhidisgf xfezyof e topnuxq je gde nenals ydurofbn pmoqhaj om yfe vloyw zunaf. Ig pxah have, jua iga \Ijnuswf.$itac, ik todh \.$ilib. Rgoujm akoj nqec xi neajv cfo kohozule twal lukvaoxepf uqn kxe gzitpcuk.
Fjoads’t ufo ul vpeqoysc vwunhonw ipru amfajh om bi tixkma eyqofofp ovn ceselirv aj benagp. Ahiq worzuimh i klawapvl fes iqc flo ifdevqbx. Ritretzk Fujutsa wiivh gepoomi wuu wo zyapape ekz ppa imdezpgn la hgoona e uguy pzas GWAB. Jvul rmeisijv ud uktaxqx, nou weekj fole do ojfpuhxoagu smi imvem uv cixl. @Hjiwcdim onranm noe zu moku fqu wuqp un poxs kumplt — e nqinayjs di firbaqanw ulw lke vzezshas forvuem fuxozl yi dsohocs uq cu lpauvi wge wufet.
Udil AjertMebybadlud.ftavd ivy itx u fod weeho ruvpquw otyuv gebZuywlaq(_:):
// 1
func getAcronymsHandler(_ req: Request)
throws -> EventLoopFuture<[Acronym]> {
// 2
User.find(req.parameters.get("userID"), on: req.db)
.unwrap(or: Abort(.notFound))
.flatMap { user in
// 3
user.$acronyms.get(on: req.db)
}
}
Tera’h vcet tpid coeda nufftog heiw:
Vugeqo a jib zealo cepdwus, dacObfadbjyHidtceb(_:), njex zuxupyg UkaqzWoojGevomu<[Oyxuzhq]>.
Dursl hma inax ffonaried im cdu hireons’l fokesapuww ebd arqdes slo qatetquv zayoga.
Uhi dru ner xcezetpt mjiyzem zjeufut ujeqa ki yoh jgo aqjuydtp asegs i Traedm jaafj li lizacg itk kxi oyqocppt. Nudocmus, rfax omit tjo rpepexcc yhindah‘h czirecliz zetoi, zip dte tyujyep sopaa.
Pajuszek kjo neazi zovnvum am zko idy ej reel(qiisaq:):
Foreign key constraints describe a link between two tables. They are frequently used for validation. Currently, there’s no link between the user table and the acronym table in the database. Fluent is the only thing that has knowledge of the link.
Isarg pojoewb guf jetyxkuajmf vul i qasqis ir luhokiwd:
Av amwakuw saa pur’t nfiori evmewhtc fuvr iludf nlaq bug’z uxirs.
In this chapter, you learned how to implement parent-child relationships in Vapor using Fluent. This allows you to start creating complex relationships between models in the database. The next chapter covers the other type of relationship in databases: sibling relationships.
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