英文:
Use Regex with NSPredicate
问题
# 目的
- 我想使用 `NSPredicate` 来使用正则表达式匹配所有以 "Test" 开头的字符串。
- 我特别想使用 `Regex` 和 `NSPredicate`。
# 问题
1. 我犯了什么错误？
2. 使用正则表达式实现我想做的事情的正确方法是什么？
# 代码 (我的尝试，不起作用)
```swift
let tests = ["Testhello", "Car", "a@b.com", "Test", "Test 123"]
let pattern = "^Test"
let predicate = NSPredicate(format: "SELF MATCHES %@", pattern)
for test in tests {
let eval = predicate.evaluate(with: test)
print("\(test) - \(eval)")
}
输出
Testhello - false
Car - false
a@b.com - false
Test - true
Test 123 - false
英文:
Aim
- Using
NSPredicateI would like to use Regex to match all strings beginning with "Test" - I specifically want to use
RegexandNSPredicate.
Questions
- What mistake am I making?
- What is the right way to use Regex to achieve what I am trying to do.
Code (My attempt, doesn't work)
let tests = ["Testhello", "Car", "a@b.com", "Test", "Test 123"]
let pattern = "^Test"
let predicate = NSPredicate(format: "SELF MATCHES %@", pattern)
for test in tests {
let eval = predicate.evaluate(with: test)
print("\(test) - \(eval)")
}
Output
Testhello - false
Car - false
a@b.com - false
Test - true
Test 123 - false
答案1
得分: 2
NSPredicate 和 MATCHES 中使用的正则表达式必须与整个字符串匹配，因此你需要使用：
let pattern = "Test.*"
或者 - 如果输入字符串中可以有多行：
let pattern = "(?s)Test.*"
以便让 .* 匹配剩余的字符串。
如果字符串必须以 Test 结尾，使用：
let pattern = "(?s).*Test"
在这里不需要使用 ^ 或 $ 锚点，因为它们在这里是隐含的。
如果字符串必须包含一个 Test 子字符串，使用：
let pattern = "(?s).*Test.*"
请注意，这不是非常高效的，因为第一个 .* 导致了高度的回溯。
英文:
The regex used with NSPRedicate and MATCHES must match the whole string, so you need to use
let pattern = "Test.*"
Or - if there can be mutliple lines in the input string:
let pattern = "(?s)Test.*"
to let the .* consume the rest of the string.
If the string must end with Test, use
let pattern = "(?s).*Test"
You do not even need the ^ or $ anchors here since they are implicit here.
If the string must contain a Test substring, use
let pattern = "(?s).*Test.*"
Note that this is not efficient though due to high backtracking caused by the first .*.
答案2
得分: 0
尝试精确匹配.... 尝试使用 MATCHES，尝试使用 LIKE 或 CONTAINS 代替。
let predicate = NSPredicate(format: "SELF CONTAINS %@", pattern)
请参阅此处以获取更多信息。
英文:
You try an exact match.... try with MATCHES, try LIKE or CONTAINS instead.
let predicate = NSPredicate(format: "SELF CONTAINS %@", pattern)
See Here as you need
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