限制一个或多个textfiled输入长度及内容

#define TEXT_MAXLENGTH11 //允许最多输入11个字符

#define TEXT_CODELENGTH 6 //允许最多输入6个字符

#define kAlphaNum @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
//仅允许输入数字和字母
#define kPhoneNum @"0123456789" //仅数字

textFiled.keyboardType = UIKeyboardTypeASCIICapable;//数字字母键盘，设置输入框仅能输入数字和字母

textFiled.keyboardType = UIKeyboardTypePhonePad;//数字，*#键盘，设置输入框仅可以输入手机号
textFiled.keyboardType = UIKeyboardTypeNumberPad;//纯数字键盘，设置输入框仅可以输入数字

下面这个方法可以控制输入大小以及仅限输入字母或数字，但是只要输入达到上限便不可删除，因为如果用户按下删除键，范围的长度就是1，并使用一个空字符串对象替换该字符。若在长度上限的位置进行删除，则直接返回NO，不可修改textField。

NSCharacterSet *cs;
cs = [[NSCharacterSet characterSetWithCharactersInString:kPhoneNum] invertedSet];
NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""]; //按cs分离出数组,数组按@""分离出字符串
BOOL canChange = [string isEqualToString:filtered];
return self.phoneText.text.length>=TEXT_MAXLENGTH?NO: canChange;

因此如果判断删除操作，便可解决无法删除的问题。

最终代码：

//textFiled代理方法
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{

NSCharacterSet *cs;
cs = [[NSCharacterSet characterSetWithCharactersInString:kPhoneNum] invertedSet];//仅允许输入数字
NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
BOOL canChange = [string isEqualToString:filtered];//判断输入是否为数字，返回0则不可以输入

if (self.phoneText.text.length>=TEXT_MAXLENGTH) {
if ([string isEqualToString:@""] && range.length > 0) {
//如果是删除按钮，则返回YES
return YES;
}
else {
if (textField.text.length - range.length + string.length > TEXT_MAXLENGTH) {
return NO;
}
else {
return YES;
}
}
}else{
return canChange;
}

}

2.设置多个TextFiled的不同输出长度.例如输入手机号和验证码。需要限制哪个TextFiled就设置哪个代理。

_textPhone.delegate = self;
_textPhone.keyboardType = UIKeyboardTypePhonePad;//只可以输入手机号的键盘
_textCode.delegate = self;
_textCode.keyboardType = UIKeyboardTypeNumberPad;//纯数字键盘

调用代理方法。通过判断输入框设置不同的输入长度以及内容

if (textField == _textPhone)

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSCharacterSet *cs;
cs = [[NSCharacterSet characterSetWithCharactersInString:kPhoneNum] invertedSet];
NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""]; //按cs分离出数组,数组按@""分离出字符串
BOOL canChange = [string isEqualToString:filtered];
NSLog(@"canchange == %d",canChange);

if (textField == _textPhone) {
if (self.textPhone.text.length>=TEXT_MAXLENGTH) {
if ([string isEqualToString:@""] && range.length > 0) {
return YES;
}
else {
if (textField.text.length - range.length + string.length > TEXT_MAXLENGTH) {
return NO;
}
else {
return YES;
}
}
}else{
return canChange;
}
}else{
if (self.textCode.text.length>= TEXT_CODELENGTH) {
if ([string isEqualToString:@""] && range.length > 0) {
return YES;
}
else {
if (textField.text.length - range.length + string.length > TEXT_CODELENGTH) {
return NO;
}
else {
return YES;
}
}
}else{
return canChange;
}
}
}