Objective-C - 【CoreData】あるEntityのあるPropertyの最大値、最小値を取得する - QiitaのSwift2.0版です。

簡単なソースコードだけ。

Persion.swift

import Foundation
import CoreData

class Person: NSManagedObject {

// Insert code here to add functionality to your managed object subclass

}

Person+CoreDataProperties.swift

import Foundation
import CoreData

extension Person {

    @NSManaged var age: NSNumber?
    @NSManaged var name: String?
    
}

Test.swift

for num in 0...10 {
	if let person = NSEntityDescription.insertNewObjectForEntityForName("Person", inManagedObjectContext: managedObjectContext) as? Person {
		let age = num * 5
		let name = "name_\(num)"
		person.age = age
		person.name = name
	}
}
/// 保存処理        
saveContext()
        
/// ここからが最大値の取得方法
let expressionAgeName = "maxAge"

/// fetchRequestの生成
let fetchRequest = NSFetchRequest()

/// EntityDescriptionの生成
let entityDescription = NSEntityDescription.entityForName("Person", inManagedObjectContext: managedObjectContext)
fetchRequest.entity = entityDescription
        
let keyPathExpression = NSExpression(forKeyPath: "age")
let expression = NSExpression(forFunction: "max:", arguments: [keyPathExpression])
let expressionDescription = NSExpressionDescription()
expressionDescription.name = expressionAgeName
expressionDescription.expression = expression
expressionDescription.expressionResultType = NSAttributeType.Integer16AttributeType
        
fetchRequest.resultType = NSFetchRequestResultType.DictionaryResultType
fetchRequest.propertiesToFetch = [expressionDescription]
        
do {
	let results = try managedObjectContext.executeFetchRequest(fetchRequest)
	if let maxAge = results.first?.valueForKey(expressionAgeName) as? Int {
		print("maxAge = \(maxAge)")
	}
} catch let error {
	print(error)
}

こんな感じで取得できました。

補足

最小値が欲しい場合は

let expression = NSExpression(forFunction: "max:", arguments: [keyPathExpression])

の部分を

let expression = NSExpression(forFunction: "min:", arguments: [keyPathExpression])

にすれば良いです。

他にも平均値のavarage:や合計のsum:、数のcount:と指定できる値があります。

終わりに

やはり僕はSwiftの方が好きです。