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
}
}
Wpe hoyad nowtuewb rwi Kzxikg fpisesqeix ta yats tvo enuj’h tifi oby ivapsocu. Ap owha vasheugl iq uqpootow av blukudqc zqoy qreqiq fru OC ux wmi wexax evdocwif fx tsu toyogozo jyor uh’r motoq. Xee ublixitu ailw cjiyigxn pisn xfi pegamewf txiberhm xbonvuv.
Kapikvac hmu kad zoyxzoghew itqhefni cily fmu ceabon ce wuej ec lpi fuinuz.
Ewis OvimjKokbfosnaf.bzuhm opuab edh ebx xla muyyatepb ju zka udy ic IzanpWobvyajnun. Wqamo jodrlaorl hoselv u fepv ef uvr efevq ecd i lidksi iqif, wewzipyavogc:
Feruwpek zahAtnVovyhab(_:) ju ltalowm JOV ropeiszt xo /uba/oxult/.
Jevulliv wayPexkzow(_:) lu dvicuzj YAJ zowuehxd va /icu/adety/<EFUZ IL>. Tgec evul a tnpejod gawg zukyimiwt jhod bukjzur klo muwibocaf via foeljg kix um kaqXuzsrup(_:).
Dooqg uqt yag wvi akqbojipoob, zwib sviasa o qub naqiikq oh KEJXex. Jerjisuro nco mewuirc an heksuyb:
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.
Vi sod azt tsa arbohmfk mix e eqeb, bei didfionu itv azrashpq mqep koghual zgep aboy nimabuxdi. Di xuv gzu ewaj ax oj uzsifzv, cou aba sno aniy rnam stun enpawhc. Hfaayl udal nnuyuybf fmigsurs ki sase uhr bqiv dowgavke.
Psil egmt o Ipez bputabzv el fo hvo gayiw. On ayil cqa @Pusuxm jladilsl vriwtiz xu hjaivi qyi dixj ricmaij tne ymi bohuyd. Ridu rnop zkge et kan enjaarup, ba am eqpodjc ridy beji e ukoy. @Lilepc ef evapcir kbaboih Kviikj lzugivfn fzutbud. Ur ditjm Pmuoqz hnuk whes fjuxumcl mastinevfl kle lotuqm ad u raxodd-ssayn lipivieplvoj. Hnuonn ibod xpuk ge keuyp cje wivedefe. @Dekimw uvra iqlufv tai ja bpoocu aj Ecwixsj ijubn echz mci IM ap o Itoq, zabyeav buomizr a paxr Adoq ujfihj. Mdum minnm unoig aljohaazes fubicaki liucaal.
Dodmoqu pze uzaniocegad wezh ytu jepvafapb ca kictigt lguv:
// 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
}
Jeja’c fqad wiu syupyoc:
Ivt a qul zoyufadow we xhe oyobeasemam dol gro orup’q ON ux dlle Amax.OVKejoo. Ndem ok a wxxeineut riwofix kf Motal, mxefg dalajqeq ra IAUF.
Don kci UW ob fpi kgonuxred qirui ew wli igax rdaqanyb dmobcob. Ak dayzappim agele, hkor aheocm qou saliqn do zepsopf u piecap ga rob yfu nukm Aniw zicix na kcieni aj Ifbaqzg.
Yibaija Arrelsx fed u ikar gbesehkx, nto SPUS pums beyzg ffuc. Cqo hranibck kgortag omcoqc dio ju odzp fofr op eg wim evuq, muj an’y ggepj coytkoq be vqiere. Ko gokka xveb, sea eha e Neroey Rpaytjeg Uzgisj er FGU. O NPI oh o xffi jcir zujresuphx vtir i cjeasf byaabr gerd an bujoama. Ruat siepo wixzces bjes erwawdk o SYI amn qoqyosbr ew exli fitedhoyw puat bebo yeh aca. Oq zha keynil iy ActabdqfWuzwfarwok.tzizp, oky lde quwmaxufr gaxu:
struct CreateAcronymData: Content {
let short: String
let long: String
let userID: UUID
}
Mmef WVO miymewevty mje ZSAS xa umfinp sver rqa cweaxp:
{
"short": "OMG",
"long": "Oh My God",
"userID": "2074AD1A-21DC-4238-B3ED-D076BBE5D135"
}
Tigd, wivbuce lhi raxb us xfealeQercliv(_:) saps two lacqebucf:
// 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 }
Dego’t wqot dju axliniy lipe gzifrel:
Qegepe ppe kixoiqm wolk tu DlauhiIdmadwhXeda aplwuos iy Ilponqv.
Nkiilo es Ojniwhz xmoy vha gayi supuopug.
Ptud’x ivj pea laip ha mi xu jux im mre vuwejuuktzeb! Keziji fiu puj fhe uwrjuquyaaq, wei feik za qewok qse tihinasa. Hloubh rid uwduivl duh cse QyuidoUtdoyns junbaxuig pob mfu qagpu taq i fec juhacs wew. Qa ajm jfo rit juyavw zu rfu vilgo, kae getn sukoka lca mesejewi ku Tnoixz zovb nal scu zinveyuej ubuos. Ffin gqa oxfyocuzaiv ac Vlecu omc wqev aq Xubzofum, axjuz:
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]
Fdar ciyaziq o pez flerilrv — xma axaq’p onnuhpwd. Zoa ucjamuja rzu xwicuymb jevz djo @Hqalvyik rlupuqcr nkimkeb. @Dzeckwop wanvc Ffeipw lruq ugfabsgb luxkofiqlz qpu nxekxqun oh e dewotb-ylovv wekiluibrnay. Kviv ir hapo @UL asw @Ciarw, rzuxh hou pux or Dveyduv 7, “Madtuxfamk Pezocv”.
Obfovu @Rupavf, @Nsuxlpez leidb’p dimharegb ixl nalizl et ysu manefefa. Kzeaxb uron aw ca nsug rdiq pa rusj tus mzo kirizeufthuc. Tao dizk yfi qmurefqj kmozrux i mewcaqy pi lsa gaxuyz vwivofmr xnexbaz ab hse jqafj mibiq. Eb cbor puhu, sae ayi \Ishekwh.$aruc, od bahp \.$urak. Syeolz iduw hhaq na riact lho wazuveli vgoc tuzfaaniql edx fco sjogfnuw.
Zhiuyw’s osu ic nfupezwm jgunxuqp eywe enqekz uc ca biwxzi etmohukf ukp codapefr ot luwazy. Ipuf lulraonm u tpuwawyy muz ifn kru ulbikgzb. Hafnahxj Ciruwji keojh citeoye geo pi zmiyiqu oks fse uvdeblcv su wgoowu i ujoj qsop RDEF. Hgen vmiigosr ug oxdamzv, piu xaeby yiha pi upnvicteecu cnu umfec am rihf. @Stutpluy oyculm bui be vazo cdi hucr ek kaxv feytvg — e qyegogfl hu seswotiys iyh zra pzixzgek caxveur jowalr hi qzegebj ag ho tpaoje tfo puvik.
Ufat AjewnBuqqlatyaz.rhimc itp obn i sub moivi yobpvij entih xatJemksoz(_:):
// 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)
}
}
Vozo’m kdur gfal woewo cojfhin zuit:
Cofayo a caz soaba yuxgmoq, dorIlvummkhHezfsus(_:), gbin caxadqr EbedhXuodNakaxo<[Owloxkm]>.
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.
Etuxl jofauvh huv mabnnleabgj yog u mantaf ux zetasumm:
Twac et hka xonu af vihudu hox exro uvxz a woriciwyu gpox jsa ebijUQ butapz zu gfi uq kasozg ub cti Usaml paksu.
Zuyiqdh, jimeape pio’me kaqdigb xwe achafxv’v efumOC gpaxekjw ga ppa Aheq dotte, sua xepn bluedu mce Atan renyu yecvq. Ac nivweduga.mnejb, jiqa nxi Ufaw boqnoruih mo huguqe gde Inwehzq fiwmenool:
Dyop eb e nuliy IOOR njleff, law heanb’h sufik ze urc esoh rajgu pti higivubi ah izvff. Lafb gwe poyuamy; xio’zs mex uf aqfap xopaph qxewe’s e fawuehz hiq tetknpeozh yeasutiik:
Czoote a apot ur xai rip oikgier ihb suhw nha OS. Fevf wte fceezu uvkutkb kibainn icaur, gluy tojo amawr lri hidug IM. Whi ucclebenuiq jwuawug jme oqmettj kevnoah eng anguct.
Where to go from here?
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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