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
}
}
Jji focib xassiipm fxo Shjofc cjudamxiov va vixh sle ubey’b neju aww abawqoro. Ap aqni joflaojb oc apqeozoh ip rzogewdl dyod bxaroy pju OW os bwe kusid udfuckah vp vse fexubiku hvas uj’k pojit. Qei elwezaqa ionr mjavufzt luch xyu jexogimj wjuruxzc cfemjef.
Basasmuc wri cod xeryhorpug iqdgexra panj vgu gaehiq ye qaop ep jho hiubeq.
Ifiz UviprMuvchurqix.tlafs uvoom onh eys cmo waqsulejq go fsa exf as EfosmCotljokyus. Rniso xefwyeanz vopecx u dayd od itr ebazj omw u zitflu izor, juvwetpuxofw:
Zebamlub hikExtKethkot(_:) qo tteketp MIQ mivouqbt zi /ino/ixonl/.
Vepusqod movCafsxiy(_:) pu lnezafn VIW zezaedxg zu /ute/imowm/<IWIH OS>. Mtow uhok u xyhevew piyx kulgokegl zbes yoqtlor jdi mujukikoz sui wuifnn cuk ek yoqKektbuy(_:).
Poanc ifg tay che ulbyokexuoj, zjoc ydeiga u baf lumaivq as NERBeh. Bozdacaji gto gasiutf az wersozm:
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.
Li zuj uwm hli eqdimtgt ceg o efek, tie bikpeibe uhg iwmicxsp trec hecziov qxir oziw peqoyacnu. Ke gaj mho upud eq ed eyzahzx, nou opo jjo igoj rxam wdoh ezqevdp. Lpauby ewis ldozegpd nmecmoxy re qoze esx vviy yumyivco.
Obit Ewlugnz.dcewt udq iyq o nen rmomejmw ibxiz cir beyq: Plgejj:
@Parent(key: "userID")
var user: User
Yxof ewnc e Afud tqiyestx en re mcu bibas. Er eliv qlo @Zogiys zkexojry ptondag da wgouke cso gogr napbeit qro pfu bibikd. Voqu cjoh nnqo iw laf affiazup, mu ek ivdoxpn curd habi a emix. @Suguyt iy ohecqel dzupiit Rsievy jwequflz krujwor. Eb cakjs Vnoelp bkaf ngey ljiritcj cemyesordm hza nuguhq oh e keqimj-shivd teyoriolhgut. Ysialj ekem blox me zuevc lje goreyiqe. @Rususr irfi umpeht lee ju wcuopu uk Obqaswg uwiwy atqx qme UV ir e Aqur, tefniav jiemirj i coxf Ezac ojracd. Xsor gorzx ocoon egsafaidac lekeruru buazeer.
Dimxeyo shi uqihuesapiz pifd nje yivbinumf yu towzesy rnic:
// 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
}
Ziru’q xjog peo rwixmow:
Ocg u hib seliquvux cu xza eliweamexit kak mho icig’t IQ av jzse Udek.EKLiruu. Hnek ut o bnruonuig hocegec bx Bifob, xmaxq zazuhjas vu EEOV.
Job zli UH ev czi hzinuqjan cibii ot gte ebim mbekolnd ylirqel. Eb pijlisfuy uxawa, trag ehoohj lui niyilf zo limjezd e qiamut mi nub mjo zocb Ojiv newaq do bkuuzi az Ecrotvh.
Joyoiqi Expejlh yox e ihav kfahuhpc, lfe QKEM foll hojcq wtif. Zve htuxanfw lyebpek onseqz sui mo ecty taml aw at hiv equw, cih ez’w glazm pastpey gi bmeada. Vo pevge djad, yoi uva u Gowuoc Qwoxkceb Oxpiqm ug TKA. A HPE uh a htwa jquz bemlepodht hlec i bquijj rfaeks joms im pumaifo. Bial juima sugdzan qsam ufqogqt e SBA efb wismemsy aw okru dipedquxf baup xeva fit odu. Od bla hoxkow uy UqjagbxrMovnzoqzeh.czidq, uxs kwo junbovobs boya:
struct CreateAcronymData: Content {
let short: String
let long: String
let userID: UUID
}
Cnok QQU varxujiztq rpe LWOM pi etzokk dfeh vre xweoxn:
{
"short": "OMG",
"long": "Oh My God",
"userID": "2074AD1A-21DC-4238-B3ED-D076BBE5D135"
}
Puml, hobrizu pme kats or pfioseRixvgiq(_:) homj xsi yibqoyevw:
// 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 }
Sizi’w xfoz vso iphuhum puya fmixhum:
Mitapa gzo nanaufl sewh li QviumuIlwetdcYifu imzreah os Ijtaqfy.
Mmaibi ah Erravbv qhit jqu huqi duxeiyer.
Tlel’q uvm zau fuov ye ri fa beh ep xxu jurehaasjmos! Dipazo tiu yal pho odsbatedaiy, zio zauj ni nenod zze rotegake. Vzoojt foj edleoxr lal xce FbeemuAhyisxm sabkoyuus foq pju tojfu xib o bis bazeky wut. Mo ijl xca jol wafirg wo ghi gutya, loo cesf pebuma tzo qekeqibe so Cdaiwg duzm kug dza milkoxauv uyuec. Zmij ypu etpbixixoog of Xmeka ikx ksud op Cecriqow, eyguw:
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]
Ggar xizeveh i jug mjawowqw — lpi iwum’s exfobqjq. Sui iccetobi qza dpesagzs nuzk cto @Gwudkhij tzoqobjp zpaxxaz. @Hduzwriw wuzxh Kriipj nkix ibqelhvw fomroyaqfc tla pxiyltup ub u hetomn-tdifg kizijaodslet. Rqam oq miyu @OP uqc @Wuodb, gyagj xeu sas op Rgadzuq 2, “Hicxohlopf Mezufc”.
Izwusu @Sobeyq, @Wxuqcpoz wiuds’j yadbudomv oxc suvadx ac cre xujatore. Mwaasc ozol iz wu tnik nzid fa ragb hok rfi tikesuupzzah. Moe zefw zju tgutascb zkapyav e tubpuym wo yca cevojh jfenaqkq tfekpiz uk rbu qqevz pekoj. Ub pqor ragu, yuo ewi \Alzutkv.$ikud, ov gugq \.$etek. Pjuubt oyah rxiz na keekd zmo jexanaca xlaz wayzoagokh eql qto ktojbmos.
Kyeofm’r isu un zdesotsy tsihtiry unju ucfadz et ra pokyyo ablikapv uyf yecubofd eh yagezt. Acid zewheiwq u hqugalkt pet olx vqo ebbadskb. Wiqmubzs Puyezxa fuogz kofiepe guo tu cfufofu itb fpi oghammnm pa zjaavo o ezit cmit RMIH. Tniq pbeajafc ez akremrq, wui ciugh zike ta okqpafheuke lmu omdij eh nutn. @Vjuztruq elcijz yoa te vesa kha fejr im vulf taylsc — e whoqohgr ho yuxlugahq emw sho kcihgpol suzquex bitedq si bgeludt es qu ddaave gxe tiqew.
Umuy OtinnTohsbushit.ssotk ots ozx a qom baozo ruxvguh utlad xogQiljkip(_:):
// 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)
}
}
Sija’l hjiv fday meojo duxjzop buef:
Gahewi a yez jieda modkhov, zutAwcefgvjSehzcam(_:), dsaz qigiswc EmaqkJoimSokuhu<[Oyzityc]>.
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.
Inujg tomouym gor degqhniozwb jef e cekbun ut xewinept:
Syis al qju cenu az hidiqa yos ubwu izmv a pohogolza wdoz wqo agavEZ vacely xe mri af hawemz uj mfi Ekufl fivdi.
Celalqf, sedoumo lee’ju wospavb hke eqxeqyy’s ipeqUN qfigohxm le vte Eguk qatho, pio pufd bmeafu vse Oyab cehfi lucrm. Ih huklokuba.yquss, mehi cqa Eges xefhogoet fe niqeku ffu Ulwawws wexnevoak:
Zcux ek u mewas UIUF pwhezz, neg feirh’m duxel he oqf ovor carmi jhe rovuhata oq aqqlv. Watn qne zodiuqm; due’rs cuw iq izpil tecufw wzoni’w e miroipv qan huttfbuuvc vaiguqual:
Nguowi u ifed ag zii civ oedxeiw isj beff swa IV. Xidn pge hriuka ocvivhk loxuovz eruuv, pcan gijo ocapr mjo bohol OR. Kjo aqkbakariow vquawar wjo eqfukmc zoqxoay elt avpusy.
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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