Flutter中如何将WordPress API返回的嵌套ArrayList转换为Model类(POJO)

Got it, let's tackle this nested array issue from the WordPress API in Flutter. That wp:term structure is a bit tricky since it's a 2D array (array of arrays of term objects), but it's totally manageable once you map it correctly to Dart types.

First, let's break down the structure: your JSON wp:term is [[{termObject}]] — so it's a list of lists of term objects. In Dart, this translates directly to List<List<Term>>, where Term is the model for the inner term data.

Step 1: Define the Inner Term Model #

First, create a model class for the individual term objects (the innermost data):

class Term {
  final int id;
  final String link;
  final String name;
  final String slug;
  final String taxonomy;

  Term({
    required this.id,
    required this.link,
    required this.name,
    required this.slug,
    required this.taxonomy,
  });

  // Manual JSON deserialization
  factory Term.fromJson(Map<String, dynamic> json) {
    return Term(
      id: json['id'] as int,
      link: json['link'] as String,
      name: json['name'] as String,
      slug: json['slug'] as String,
      taxonomy: json['taxonomy'] as String,
    );
  }

  // Optional: Convert back to JSON
  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'link': link,
      'name': name,
      'slug': slug,
      'taxonomy': taxonomy,
    };
  }
}

Step 2: Add the Nested List to Your Parent Model #

Next, in your parent model (e.g., Post for a WordPress post), define the wpTerm field as List<List<Term>> and handle the nested deserialization.

Option 1: Manual Deserialization #

If you prefer not to use code generation packages, handle the nested array directly in the parent model's fromJson factory:

class Post {
  // Add your other post fields here (e.g., id, title, content)
  final List<List<Term>> wpTerm;

  Post({
    // Initialize other fields...
    required this.wpTerm,
  });

  factory Post.fromJson(Map<String, dynamic> json) {
    // Extract the nested wp:term array
    final wpTermRaw = json['wp:term'] as List<dynamic>;

    // Convert the 2D array to List<List<Term>>
    final List<List<Term>> wpTermList = wpTermRaw.map((innerList) {
      return (innerList as List<dynamic>)
          .map((termJson) => Term.fromJson(termJson as Map<String, dynamic>))
          .toList();
    }).toList();

    return Post(
      // Initialize other fields from json...
      wpTerm: wpTermList,
    );
  }
}

Option 2: Use json_serializable (Code Generation) #

If you use the popular json_serializable package for serialization, it can handle the nested list automatically with a small tweak for the field name.

1. First, add dependencies to your pubspec.yaml:

dependencies:
  json_annotation: ^4.8.1

dev_dependencies:
  build_runner: ^2.4.4
  json_serializable: ^6.7.0

2. Update the Term model for code generation:

import 'package:json_annotation/json_annotation.dart';

part 'term.g.dart';

@JsonSerializable()
class Term {
  final int id;
  final String link;
  final String name;
  final String slug;
  final String taxonomy;

  Term({
    required this.id,
    required this.link,
    required this.name,
    required this.slug,
    required this.taxonomy,
  });

  factory Term.fromJson(Map<String, dynamic> json) => _$TermFromJson(json);
  Map<String, dynamic> toJson() => _$TermToJson(json);
}

3. Update the parent Post model, using @JsonKey to map the wp:term JSON key to your Dart field:

import 'package:json_annotation/json_annotation.dart';
import 'term.dart';

part 'post.g.dart';

@JsonSerializable()
class Post {
  // Other post fields...
  @JsonKey(name: 'wp:term')
  final List<List<Term>> wpTerm;

  Post({
    // Initialize other fields...
    required this.wpTerm,
  });

  factory Post.fromJson(Map<String, dynamic> json) => _$PostFromJson(json);
  Map<String, dynamic> toJson() => _$PostToJson(json);
}

4. Run the code generation command in your terminal:

flutter pub run build_runner build

Key Notes #

• The List<List<Term>> type matches the JSON's 2D array structure perfectly. Each inner list typically represents a taxonomy type (e.g., one list for categories, another for tags).
• If you ever need to access the terms, you can loop through the outer list to get each taxonomy group, then loop through the inner list for individual terms.

内容的提问来源于stack exchange，提问作者Sunil