Question 243206 in Flutter Question posted in
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Flutter – the argument type 'string ' can't be assigned to the parameter type 'pattern'

I have a problem that the argument type string can’t be assigned to the parameter type pattern in this code I added the null check ! but the error didn’t disappear what shall I do? in this problem i coufused the error in this line
caculStr = caculStr.replaceFirst(inlayMethod.firstMatch(caculStr)?.group(0), ‘caculStrTemp$i’);

  Future<dynamic> handleCalcuStr(String caculStr) async {
var temp = new Map();
if (matrixs.containsKey(caculStr)) {
  return matrixs[caculStr];
}
if (dbs.containsKey(caculStr)) {
  return dbs[caculStr];
}
if (num.tryParse(caculStr) != null) {
  return num.tryParse(caculStr);
}
if (ufTemp.containsKey(caculStr)) {
  return ufTemp[caculStr];
}
caculStr = formatCmdStr(caculStr);
if (caculStr.contains('(')) {
  var caculStrs = [];
  int index = -1;
  List<String> stack = [];
  for (int i = 0; i < caculStr.length; i++) {
    if (caculStr[i] == '(') {
      if (stack.length == 0) {
        caculStrs.add(new StringBuffer());
        index++;
      }
      stack.add('(');
      if (stack.length == 1) {
        continue;
      }
    }
    if (caculStr[i] == ')') {
      stack.removeLast();
      if (stack.length == 0) continue;
    }
    if (stack.length != 0) {
      caculStrs[index].write(caculStr[i]);
    }
  }

  if (caculStrs.length != 0) {
    for (int i = 0; i < caculStrs.length; i++) {
      RegExp inlayMethod = new RegExp(r'[A-Za-z]+(' +
          caculStrs[i]
              .toString()
              .replaceAll('+', '\+')
              .replaceAll('*', '\*')
              .replaceAll('(', '\(')
              .replaceAll(')', '\)') +
          r')');
      if (inlayMethod.hasMatch(caculStr)) {
        temp['caculStrTemp$i'] = await _invocationMethod(
            inlayMethod.firstMatch(caculStr)!.group(0).toString());
        caculStr = caculStr.replaceFirst(inlayMethod.firstMatch(caculStr)?.group(0), 'caculStrTemp$i');
        continue;
      }
      caculStr = caculStr.replaceFirst(
          '(' + caculStrs[i].toString() + ')', 'caculStrTemp$i');
      temp['caculStrTemp$i'] =
          await handleCalcuStr(caculStrs[i].toString());
    }
  }
}
Tags:

2

Answers


  1. 0

    This is because replaceFirst expects a Pattern instead of a String as its first argument. The Pattern class is thesuper class of RegExp class. So you can pass a RegExp obkect as the first argument to the replaceFirst method.
    Try changing that line to

    caculStr = caculStr.replaceFirst(RegExp(inlayMethod.firstMatch(caculStr)?.group(0)), 'caculStrTemp$i');

    Shoud fix it.

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  2. 0

    The root issue seems to be that replaceFirst() expects a RegExp pattern as the first argument, but we are passing it a string by calling inlayMethod.firstMatch(caculStr).group(0).

    To fix this, we need to pass the actual RegExp pattern itself to replaceFirst(), not the matched string:

    if (inlayMethod.hasMatch(caculStr)) {
  RegExpPattern pattern = inlayMethod.pattern;
  
  temp['caculStrTemp$i'] = await _invocationMethod(
      inlayMethod.firstMatch(caculStr)!.group(0).toString());
      
  caculStr = caculStr.replaceFirst(pattern, 'caculStrTemp$i');

  continue;
}

    Here we get the pattern directly from the RegExp itself and pass that to replaceFirst().

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