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Initialize an Instance with Type in Dart

How to create a new object instance from a TypeWhat are POD types in C++?What's the canonical way to check for type in Python?How to determine a Python variable's type?What are the differences between type() and isinstance()?How to check for type errors in dartdart extend string type for type checkingDart: Create method from stringWhy are incorrect type assignments allowed in Dart?Dart - Type Conflicts

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0

Assume I have some Type instances:

final strType = String;
final intType = int;

I want to initialize instances of the Types, for example, preferably,

final myString = strType(); // myString is String()

or

final myInt = new intType(); // myInt is int()

However, the compiler raised an error of strType isn't a function.

Is it possible to initialize an instance of a Type in Dart?

types dart flutter

share|improve this question

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

add a comment | 

0

Assume I have some Type instances:

final strType = String;
final intType = int;

I want to initialize instances of the Types, for example, preferably,

final myString = strType(); // myString is String()

or

final myInt = new intType(); // myInt is int()

However, the compiler raised an error of strType isn't a function.

Is it possible to initialize an instance of a Type in Dart?

types dart flutter

share|improve this question

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

add a comment | 

Assume I have some Type instances:

final strType = String;
final intType = int;

I want to initialize instances of the Types, for example, preferably,

final myString = strType(); // myString is String()

or

final myInt = new intType(); // myInt is int()

However, the compiler raised an error of strType isn't a function.

Is it possible to initialize an instance of a Type in Dart?

types dart flutter

share|improve this question

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

final strType = String;
final intType = int;

final myString = strType(); // myString is String()

final myInt = new intType(); // myInt is int()

types dart flutter

types dart flutter

share|improve this question

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

share|improve this question

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

asked Mar 9 at 4:08

KeroppiMomoKeroppiMomo

6326

2 Answers
2

active

oldest

votes

1

This is not possible at the language level. It is possible with reflection, but the code will be complex and to use it on the web or flutter it would require codegen.

Instead of assigning a Type to a variable, consider assigning a function type. () => SomeClassName() is an anonymous function that can create an instance of SomeClassName.

share|improve this answer

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

add a comment | 

0

Yes, this is possible but not for predefined (builtin) types (classes). Because these types (classes) may don't declare default contructors.

Below is example how to use user defined types (via classes).

import 'dart:mirrors';

void main() 
 var fooType = Foo;
 var myFoo = reflectClass(fooType).newInstance(const Symbol(''), []).reflectee;
 print(myFoo.baz);


class Foo 
 int baz = 41;

Result:

41

share|improve this answer

answered Mar 9 at 6:51

mezonimezoni

4,18221631

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for your answer, but I did some research and found out that dart:mirror is not available in flutter. Am I correct, or are there any other ways to achieve this?
  
  – KeroppiMomo
  Mar 9 at 7:07
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You can always ask new question. Eg, about how to use (any kind of) reflection in Flutter. Because dart:mirrors library is a reflection library but it's not the only library of such kind.
  
  – mezoni
  Mar 9 at 11:44
  

  
  
  
  

add a comment | 

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1

This is not possible at the language level. It is possible with reflection, but the code will be complex and to use it on the web or flutter it would require codegen.

Instead of assigning a Type to a variable, consider assigning a function type. () => SomeClassName() is an anonymous function that can create an instance of SomeClassName.

share|improve this answer

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

add a comment | 

1

This is not possible at the language level. It is possible with reflection, but the code will be complex and to use it on the web or flutter it would require codegen.

Instead of assigning a Type to a variable, consider assigning a function type. () => SomeClassName() is an anonymous function that can create an instance of SomeClassName.

share|improve this answer

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

add a comment | 

This is not possible at the language level. It is possible with reflection, but the code will be complex and to use it on the web or flutter it would require codegen.

Instead of assigning a Type to a variable, consider assigning a function type. () => SomeClassName() is an anonymous function that can create an instance of SomeClassName.

share|improve this answer

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

share|improve this answer

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

answered Mar 9 at 17:35

Nate BoschNate Bosch

1,246811

0

Yes, this is possible but not for predefined (builtin) types (classes). Because these types (classes) may don't declare default contructors.

Below is example how to use user defined types (via classes).

import 'dart:mirrors';

void main() 
 var fooType = Foo;
 var myFoo = reflectClass(fooType).newInstance(const Symbol(''), []).reflectee;
 print(myFoo.baz);


class Foo 
 int baz = 41;

Result:

41

share|improve this answer

answered Mar 9 at 6:51

mezonimezoni

4,18221631

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for your answer, but I did some research and found out that dart:mirror is not available in flutter. Am I correct, or are there any other ways to achieve this?
  
  – KeroppiMomo
  Mar 9 at 7:07
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You can always ask new question. Eg, about how to use (any kind of) reflection in Flutter. Because dart:mirrors library is a reflection library but it's not the only library of such kind.
  
  – mezoni
  Mar 9 at 11:44
  

  
  
  
  

add a comment | 

0

Yes, this is possible but not for predefined (builtin) types (classes). Because these types (classes) may don't declare default contructors.

Below is example how to use user defined types (via classes).

import 'dart:mirrors';

void main() 
 var fooType = Foo;
 var myFoo = reflectClass(fooType).newInstance(const Symbol(''), []).reflectee;
 print(myFoo.baz);


class Foo 
 int baz = 41;

Result:

41

share|improve this answer

answered Mar 9 at 6:51

mezonimezoni

4,18221631

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for your answer, but I did some research and found out that dart:mirror is not available in flutter. Am I correct, or are there any other ways to achieve this?
  
  – KeroppiMomo
  Mar 9 at 7:07
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You can always ask new question. Eg, about how to use (any kind of) reflection in Flutter. Because dart:mirrors library is a reflection library but it's not the only library of such kind.
  
  – mezoni
  Mar 9 at 11:44
  

  
  
  
  

add a comment | 

Yes, this is possible but not for predefined (builtin) types (classes). Because these types (classes) may don't declare default contructors.

Below is example how to use user defined types (via classes).

import 'dart:mirrors';

void main() 
 var fooType = Foo;
 var myFoo = reflectClass(fooType).newInstance(const Symbol(''), []).reflectee;
 print(myFoo.baz);


class Foo 
 int baz = 41;

Result:

41

share|improve this answer

answered Mar 9 at 6:51

mezonimezoni

4,18221631

import 'dart:mirrors';

void main() 
 var fooType = Foo;
 var myFoo = reflectClass(fooType).newInstance(const Symbol(''), []).reflectee;
 print(myFoo.baz);


class Foo 
 int baz = 41;

share|improve this answer

answered Mar 9 at 6:51

mezonimezoni

4,18221631

answered Mar 9 at 6:51

mezonimezoni

4,18221631

answered Mar 9 at 6:51

mezonimezoni

4,18221631