What is a NoSuchMethodError and how do I fix it?

A NoSuchMethodError in Dart happens when your code tries to call a method or property that doesn’t exist on an object.
This usually occurs because the variable is null or has the wrong type.

String? name;
print(name.length); // ❌ Throws NoSuchMethodError

Approaches

Approach A: Check for null before accessing properties

Use null checks or the null-aware operator (?.) to avoid calling methods on null.

String? name;
print(name?.length); // ✅ Prints null instead of crashing

This prevents the app from crashing when a value is missing.

Approach B: Verify the object type

If you’re using dynamic or type casting, make sure the variable is the type you expect.

dynamic value = 'hello';

if (value is String) {
  print(value.toUpperCase()); // ✅ Safe
}

Using is checks or explicit typing helps avoid runtime errors.

Approach C: Fix typos and missing imports

Sometimes the error appears because of a misspelled method or a missing import.

// ❌ Typo
user.pritnName();

// ✅ Correct
user.printName();

Check both spelling and imports.

Decision Guide

Null values: Add ?., ??, or if checks.
Type mismatch: Ensure the variable is the right type.
Missing method: Fix spelling or imports.

Avoid using dynamic unless necessary — static typing catches most issues early.

Recommendation

Use sound null safety and strict typing.
They help Dart detect these errors before runtime.

class User {
  final String name;
  User(this.name);
}

void main() {
  final user = User('Alex');
  print(user.name); // ✅ Guaranteed non-null
}

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