在發送網絡請求時，由于用戶輸入了emoji表情，服務端返回錯誤提示信息。為了解決服務器不能驗證emoji編碼的問題，需要在本地進行emoji的輸入控制（正常情況下應該由服務器在數據庫中添加emoji對應的轉碼表以支持客戶端發送emoji表情），在網上搜了下iOS端解決辦法如下：
1.當用戶切換鍵盤為Emoji表情時，輸入的表情不響應（即表情符號不顯示到UITextView或UITextField）。這里可以通過UITextView或UITextField的回調和是否為emoji鍵盤：

[[[textView textInputMode] primaryLanguage] isEqualToString:@"emoji"]
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    //不支持系統表情的輸入
    if ([[[UITextInputMode currentInputMode ]primaryLanguage] isEqualToString:@"emoji"]) {
        return NO;
    }
    return YES;
}

2.通過過濾用戶輸入的emoji來實現

//過濾表情
+ (NSString *)filterEmoji:(NSString *)string {
    NSUInteger len = [string lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
    const char *utf8 = [string UTF8String];
    char *newUTF8 = malloc( sizeof(char) * len );
    int j = 0;

    //0xF0(4) 0xE2(3) 0xE3(3) 0xC2(2) 0x30---0x39(4)
    for ( int i = 0; i < len; i++ ) {  
        unsigned int c = utf8;
        BOOL isControlChar = NO;
        if ( c == 4294967280 ||
            c == 4294967089 ||
            c == 4294967090 ||
            c == 4294967091 ||
            c == 4294967092 ||
            c == 4294967093 ||
            c == 4294967094 ||
            c == 4294967095 ||
            c == 4294967096 ||
            c == 4294967097 ||
            c == 4294967088 ) {
            i = i + 3;
            isControlChar = YES;
        }
        if ( c == 4294967266 || c == 4294967267 ) {
            i = i + 2;
            isControlChar = YES;
        }
        if ( c == 4294967234 ) {
            i = i + 1;
            isControlChar = YES;
        }
        if ( !isControlChar ) {
            newUTF8[j] = utf8;
            j++;
        }
    }
    newUTF8[j] = '\0';
    NSString *encrypted = [NSString stringWithCString:(const char*)newUTF8
                                             encoding:NSUTF8StringEncoding];
    free( newUTF8 );
    return encrypted;
}

3.通過判斷用戶輸入的字符串時候含有表情來進行對應的操作

+ (NSString *)filterEmoji:(NSString *)string {
    NSUInteger len = [string lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
    const char *utf8 = [string UTF8String];
    char *newUTF8 = malloc( sizeof(char) * len );
    int j = 0;

    //0xF0(4) 0xE2(3) 0xE3(3) 0xC2(2) 0x30---0x39(4)
    for ( int i = 0; i < len; i++ ) {  
        unsigned int c = utf8;
        BOOL isControlChar = NO;
        if ( c == 4294967280 ||
            c == 4294967089 ||
            c == 4294967090 ||
            c == 4294967091 ||
            c == 4294967092 ||
            c == 4294967093 ||
            c == 4294967094 ||
            c == 4294967095 ||
            c == 4294967096 ||
            c == 4294967097 ||
            c == 4294967088 ) {
            i = i + 3;
            isControlChar = YES;
        }
        if ( c == 4294967266 || c == 4294967267 ) {
            i = i + 2;
            isControlChar = YES;
        }
        if ( c == 4294967234 ) {
            i = i + 1;
            isControlChar = YES;
        }
        if ( !isControlChar ) {
            newUTF8[j] = utf8;
            j++;
        }
    }
    newUTF8[j] = '\0';
    NSString *encrypted = [NSString stringWithCString:(const char*)newUTF8
                                             encoding:NSUTF8StringEncoding];
    free( newUTF8 );
    return encrypted;
}

4. emoji在NSUTF8StringEncoding編碼下占用4個字節，中文編碼占用3個字節,可以根據- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string方法，把string做處理，依據

NSUInteger stringUtf8Length = [string lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
if(stringUtf8Length >= 4 && (stringUtf8Length / string.length != 3)) {
return NO;
}

判斷,可排出大多數表情符號，還有少量的符號排除不了，比如^_ ，占3個字符。
代碼不實用在九宮格鍵盤上的，可以在輸入時打斷點查看內容或直接輸出%x查看。