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📝 [Flutter] learning to form a record, [programmer essential knowledge]

📔 — Dart data type list&Map!

1. Write at the front

The string in Dart’s base data type was introduced in the previous article, so let’s move on to learning about arrays (list) and dictionaries (Map) in Dart’s base syntax.

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Dart uses var, final, and const

Dart Indicates the num of the data type

Dart String of data type

This is an array of books.

Dart lists, which are the equivalent of arrays in OC, are mutable and immutable.

2.1 the variable list

Without further ado, directly on the code, as follows:

void main(a){

  listTest();

}
void listTest(a){
  // Create a list directly
  List a = ["1".2."3.0".4.0];
  print(a);
/ / var
  var list = [1.2."zjp".3.0];
  print(list);

}
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  • The default values are variable, and you can add different data types to the list, which is very convenient.

2.1.1 Obtaining the specified subscript data

// Get the specified subscript data directly
  print(list[3]);
  // Modify the specified subscript data directly
  list[3] = "reno";
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2.1.2 Method of Inserting data

 / / insert
  list.insert(1."hellow");//list.insert(index, element)
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2.1.3 Deleting Data

 / / delete
  list.remove(1);
  print(list);
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2.1.4 Method of clearing data

list.clear();
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  • The test results are as follows:

2.1.5 Sorting method

Dart is annotated in the same way that you can view a class on iOS: Command + mouse click.

2.2 Immutable List

  • immutablelist I just add it out frontconstHere it is:

If we add const to the list, it is immutable. We cannot modify the data in the list or we will get an error.

3. Map

3.1 variable Map

In DART, a map is a key-value pair, which is the same as a dictionary in OC.

  • Create a Map
void mapTest(a){
  Map a = {"a":1."b":2};
  print(a);

  var a1 = {"a1":1."a2":2};
  print(a1);
}
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  • The running results are as follows:

3.1.1 Map Value and Changed Value

 print(a["a"]);/ / value
  a["a"] = "aa";/ / value
  print(a["a"]);
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3.1.2 map length

 / / the length of the map
  print(a.length);
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3.1.3 Map All keys

 // Get all keys
  print(a.keys);
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3.1.4 Map All values

  // Get all values
  print(a.values);
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  • The test results are as follows:

3.2 Map cannot be changed

An immutable map cannot modify key/value pairs as a list does.

  • A list can be converted into a map
print(b.asMap());/ / the list to the map
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  • The results are as follows:

More methods can be found in specific classes.

4. Write in the back

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