在利用CoreData来存储数据的时候，如果需要过滤出我们需要的结果怎么办呢？

NSPredicate

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@interface NSPredicate : NSObject

where to use

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@FetchRequest(entity: , sortDescriptors: , predicate: , animation: )

Usage

init

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NSPredicate(format: "universe == 'Star'"))
NSPredicate(format: "universe == %@", "Star"))

%@是占位符

Comparison

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grade == "7"
firstName like "Shaffiq"

==和like关键字都可以，此外还有<或>

Involve

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"universe IN %@", ["Aliens", "Firefly", "Star Trek"]
"name contains[c] %@", "Star"

(In the example, like[cd] is a modified “like” operator that is case-insensitive and diacritic-insensitive.)

more to see Predicate Format String Syntax

Regex

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"name matches %@", "[0-9]o{2}"

Logic

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"name BEGINSWITH %@", "E"
"name ENDSWITH %@", "E"

还可以使用NOT AND OR等基础关键字

Advanced

To see Predicate Programming Guide