NSPredicate验证：a-z，0-9和下划线

Question

我想只允许a-z，0-9和_（下划线），但它无法正常工作。

NSString *test = @"name_test09"; // should be valid
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", @"[a-z0-9_]"];

if ([predicate evaluateWithObject:test] == NO) {
    // not validated
} else {
    // validated
}

Answer 1

应该是。

NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES[c] %@", @"[a-z][0-9]_"];

我的编辑：

NSString *s =@"abcdefghijklmnopqrstuvwxyz1234567890_";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES[c] %@",s];

或

NSString *myRegex = @"[a-z0-9_]*"; 
NSPredicate *myTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", myRegex]; 
BOOL valid = [myTest evaluateWithObject: test];
if (valid)
{
}
else
{
}