当我加载一个UIView时,我如何在iPhone SDK上设置UITextField的最大字符数?
当前回答
稍微超出了回答原来的问题,并扩展了Frouo的答案,这里有扩展来修剪空白字符串和最大长度,并利用这些字符串扩展来修剪UITextField到最大长度:
// In String_Extensions.swift
extension String {
func trimmedString() -> String {
var trimmedString = self.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
let components = trimmedString.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).filter { count($0) > 0 }
return " ".join(components)
}
func trimmedStringToMaxLength(maxLength: Int) -> String {
return trimmedString().substringToIndex(advance(startIndex, min(count(self), maxLength))).trimmedString()
}
}
// In UITextField_Extensions.swift
private var maxLengthDictionary = [UITextField : Int]()
private var textFieldMaxLength = 20
extension UITextField {
@IBInspectable var maxLength: Int {
get {
if let maxLength = maxLengthDictionary[self] {
return maxLength
} else {
return textFieldMaxLength
}
}
set {
maxLengthDictionary[self] = newValue < textFieldMaxLength + 1 ? newValue : textFieldMaxLength
}
}
func trimAndLimitToMaxLength() {
text = text.trimmedStringToMaxLength(maxLength)
}
}
let someTextField = UITextField()
let someString = " This is a string that is longer than allowable for a text field. "
someTextField.text = someString
someTextField.trimAndLimitToMaxLength()
println(someTextField.text) // Prints "This is a string tha"
let anotherTextField = UITextField()
anotherTextField.maxLength = 5
anotherTextField.text = someString
anotherTextField.trimAndLimitToMaxLength()
println(anotherTextField.text) // Prints "This"
trimAndLimitToMaxLength() could be used in UITextFieldDelegate's textFieldDidEndEditing(_:) so that a user could enter or paste in a longer than acceptable string and then shorten it vs. just cutting off the input at the max length. In doing this, I would also set attributed text styles to indicate any portion of the text that goes beyond the acceptable length (e.g., [NSBackgroundColorAttributeName : UIColor.redColor(), NSForegroundColorAttributeName : UIColor.whiteColor(), NSStrikethroughStyleAttributeName : NSNumber(int: 1)]
其他回答
我模拟实际的字符串替换,计算未来字符串的长度:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
if([newString length] > maxLength)
return NO;
return YES;
}
下面的代码类似于sickp的答案,但是正确地处理复制-粘贴操作。如果尝试粘贴超过限制的文本,下面的代码将截断文本以符合限制,而不是完全拒绝粘贴操作。
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
static const NSUInteger limit = 70; // we limit to 70 characters
NSUInteger allowedLength = limit - [textField.text length] + range.length;
if (string.length > allowedLength) {
if (string.length > 1) {
// get at least the part of the new string that fits
NSString *limitedString = [string substringToIndex:allowedLength];
NSMutableString *newString = [textField.text mutableCopy];
[newString replaceCharactersInRange:range withString:limitedString];
textField.text = newString;
}
return NO;
} else {
return YES;
}
}
Swift 3版本 //*****这将不工作与Swift 2.x!* * * * * / /
首先创建一个新的Swift文件:TextFieldMaxLength.swift, 然后添加下面的代码:
import UIKit
private var maxLengths = [UITextField: Int]()
extension UITextField {
@IBInspectable var maxLength: Int {
get {
guard let length = maxLengths[self]
else {
return Int.max
}
return length
}
set {
maxLengths[self] = newValue
addTarget(
self,
action: #selector(limitLength),
for: UIControlEvents.editingChanged
)
}
}
func limitLength(textField: UITextField) {
guard let prospectiveText = textField.text,
prospectiveText.characters.count > maxLength
else {
return
}
let selection = selectedTextRange
let maxCharIndex = prospectiveText.index(prospectiveText.startIndex, offsetBy: maxLength)
text = prospectiveText.substring(to: maxCharIndex)
selectedTextRange = selection
}
}
然后你会看到在故事板一个新的字段(最大长度)当你选择任何TextField
如果你还有更多问题,请查看这个链接:http://www.globalnerdy.com/2016/05/18/ios-programming-trick-how-to-use-xcode-to-set-a-text-fields-maximum-length-visual-studio-style/
使用接口构建器,您可以在任何函数中链接并获得“编辑更改”的事件。 现在你可以检查长度
- (IBAction)onValueChange:(id)sender
{
NSString *text = nil;
int MAX_LENGTH = 20;
switch ([sender tag] )
{
case 1:
{
text = myEditField.text;
if (MAX_LENGTH < [text length]) {
myEditField.text = [text substringToIndex:MAX_LENGTH];
}
}
break;
default:
break;
}
}
有通用的解决方案设置最大长度在Swift。 通过IBInspectable,你可以在Xcode属性检查器中添加新的属性。
import UIKit
private var maxLengths = [UITextField: Int]()
extension UITextField {
@IBInspectable var maxLength: Int {
get {
guard let length = maxLengths[self]
else {
return Int.max
}
return length
}
set {
maxLengths[self] = newValue
addTarget(
self,
action: Selector("limitLength:"),
forControlEvents: UIControlEvents.EditingChanged
)
}
}
func limitLength(textField: UITextField) {
guard let prospectiveText = textField.text
where prospectiveText.characters.count > maxLength else {
return
}
let selection = selectedTextRange
text = prospectiveText.substringWithRange(
Range<String.Index>(prospectiveText.startIndex ..< prospectiveText.startIndex.advancedBy(maxLength))
)
selectedTextRange = selection
}
}
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