Swift-NSPredicate学习整理

Cocoa框架中的NSPredicate用于查询，原理和用法都类似于SQL中的where，作用相当于数据库的过滤取

初始化的方式:

NSPredicate(format:"")

用法

1.检索值是否存在一个范围区间里

var number2 = 0
var numberPre2 = NSPredicate(format: "SELF BETWEEN{1,5}")
var bool2 = numberPre2.evaluateWithObject(number2)

打印结果

当number2 = 0 打印：bool2 为false
当number2 = 1 打印：bool2 为true

2.检索数组元素中是否包含给定字符串

var number2 = "dd"
var numberPre2 = NSPredicate(format: "SELF IN {'dd','bb'}")
var bool2 = numberPre2.evaluateWithObject(number2)

其中出现的关键字
(BETWEEN、IN)称为范围运算符

SELF表示的是字符串本身，在本例代码中相当于变量number2

当然以数组的形式初始化NSPredicate也是可以的

var sets = ["dd","ss"]
var numberPre2 = NSPredicate(format: "SELF IN %@",sets)

3.字符串操作相关

1>判断字符串中是否包含另一个字符串CONTAINS

var str3 = "dd"
var pre3 = NSPredicate(format: "SELF CONTAINS[cd] %@", str3)
var bool3 = pre3.evaluateWithObject("dsadd")

打印结果

当str3="da" 打印：bool3=false
当str3="dd" 打印：bool3=true

2>判断是否以某个字符串开头BEGINSWITH

var str3 = "dd"
var pre3 = NSPredicate(format: "SELF BEGINSWITH[cd] %@", str3)
var bool3 = pre3.evaluateWithObject("ddacd")

打印结果

当str3="da" 打印：bool3=false
当str3="dd" 打印：bool3=true

3>判断是否以某个字符串结尾ENDSWITH

var str3 = "dd"
var pre3 = NSPredicate(format: "SELF ENDSWITH[cd] %@", str3)
var bool3 = pre3.evaluateWithObject("dcadd")

打印结果

当str3="da" 打印：bool3=false
当str3="dd" 打印：bool3=true

注：
[c]不区分大小写
[d]不区分发音符号即没有重印符号
[cd]表示即不区分大小写，也不区分发音符号

4.模糊查询LINK通配符

5.正则表达式MATCHES

//匹配纯数字
var number = "^[0-9]+$"
var numberPre = NSPredicate(format: "SELF MATCHES %@", number)
var boo3 = numberPre.evaluateWithObject("13140000000")

打印结果为 true

6.基本操作符运算

let predicate = NSPredicate(format: "(SELF > 20) AND (SELF < 30)") 
let boo7 = predicate.evaluateWithObject(num)
print(boo7)

打印结果

当num = 20 打印：false
当num = 21 打印：true

实际应用

1.检索一个数组中所有包含此字符串的元素，并返回一个结果的数组

let arr4 = ["beijing" , "shanghai" , "guangzhou" , "wuhan"] asNSMutableArray
let str4 = "ang"
let pre4 = NSPredicate(format: "SELF CONtAINS %@", str4)
arr4.filterUsingPredicate(pre4)

打印arr4 结果为

["shanghai","guangzhou"]

2.判断字符串首字符是否为字母

let regex1 = "[A-Za-z]+"
let pre5 = NSPredicate(format: "SELF MATCHES %@" , regex1)
let bool5 = pre5.evaluateWithObject("2")

3.字符串替换

//方法调用需要做异常处理
do{

        let pattern = "(encoding=\")[^\"]+(\")"
        let regex = try NSRegularExpression(pattern:
pattern , options:NSRegularExpressionOptions.CaseInsensitive)
        let sample = "<xml encoding=\"abc\"></xml><xml
encoding=\"def\"></xml><xml encoding=\"ttt\"></xml>"
        print(sample)
        let result = regex.stringByReplacingMatchesInString(sample, options: NSMatchingOptions.ReportProgress, range: NSMakeRange(0, sample.characters.count), withTemplate: "$1utf-8$2")
        print(result)
    }catch{
        print(error) 
    }

打印结果为

<xml encoding="abc"></xml><xml encoding="def"></xml><xml encoding="ttt"></xml>
<xml encoding="utf-8"></xml><xml encoding="utf-8"></xml><xml encoding="utf-8"></xml>

4.提取字符串

//组装一个字符串，需要把里面的网址解析出来
//方法调用需要做异常处理
  do{
        let urlString = "<meta/><link/><title>1Q84BOOK1</title></head><body>"
        let pattern = "(?<=title\\>).*(?=</title)"
        let regex = try NSRegularExpression(pattern: pattern , options: NSRegularExpressionOptions.CaseInsensitive)
        let firstMatch = regex.firstMatchInString(urlString, options: NSMatchingOptions.ReportProgress, range: NSMakeRange(0, urlString.characters.count))
        if firstMatch != nil {
            let resultRange = firstMatch?.rangeAtIndex(0)
            let result = (urlString as NSString).substringWithRange(resultRange!)
            print(result) 
        }
    }catch{
     print(error)
    }

打印结果

"1Q84BOOK1"

本文从一路平整理，需要了解OC-NSPredicate的读者，请点击一路平查看

Swift-NSPredicate学习整理

用法

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