switch_when
A function library that provides a more advanced switch, does not restrict Case expressions to be constants, similar to kotlin's when method.
Getting Started
Add dependency
dependencies:
switch_when: ^0.0.1 #please use the latest version on pub
Use Library
- import package Where you need to use the Library library, import the package
import 'package:switch_when/switch_when.dart';
- Use functions Different methods are used according to different situations. For general situations, you can use the when method or whenValue method. If you want the type of the returned result to be null safe, you can use the whenSafe method or whenValueSafe method.
@override
void initState() {
_curtainAnimationImage = TweenImageWidget(
ImagesEntry(1, 20, "equipmentcontrol_pic_curtain%s".toAssetImg()),
durationMilliseconds: 5000,
repeat: false,
);
super.initState();
}
Functions:
//Not Safe
T? whenString<T>(String value, Map<String, ValueGetter<T>> conditionMap)
T? whenInt<T>(int value, Map<int, ValueGetter<T>> conditionMap)
T? whenDouble<T>(double value, Map<double, ValueGetter<T>> conditionMap)
T? whenBool<T>(bool value, List<Tuple2<bool, ValueGetter<T>>> conditionList)
T? whenValue<V, T>(V value, Map<V, ValueGetter<T>> conditionMap)
T? when<T>(Map<bool, ValueGetter<T>> conditionMap)
T? whenTrue<T>(Map<ValueGetter<bool>, ValueGetter<T>> conditionMap)
//Safe
T whenStringSafe<T>(String value, Map<String, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T whenIntSafe<T>(int value, Map<int, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T whenDoubleSafe<T>(double value, Map<double, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T? whenBoolSafe<T>(bool value, List<Tuple2<bool, ValueGetter<T>>> conditionList, {ValueGetter<T>? defaultValue})
T whenValueSafe<V, T>(V value, Map<V, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T whenSafe<T>(Map<bool, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T whenTrueSafe<T>(Map<ValueGetter<bool>, ValueGetter<T>> conditionMap, {ValueGetter<T>? defaultValue})
T? whenString
Used to replace the [switch] method, because in some scenarios, an error warning of Case expressions must be constant;
If there is [value] in [Map.keys] of [conditionMap], execute its corresponding [ValueGetter] method
example:
int? index = whenString<int>("banana🍌", {
"water" + "melon": () {
return 1;
},
"apple": () {
return 2;
},
"orange": () {
return 3 ;
},
"banana" + "🍌": () {
return 4;
},
"grape": () {
return 5;
},
});
T? whenInt
Used to replace the [switch] method, because in some scenarios, an error warning of Case expressions must be constant;
If there is [value] in [Map.keys] of [conditionMap], execute its corresponding [ValueGetter] method
example:
String? status = whenInt<String>(1, {
1: () {
return "good";
},
1 + 1: () {
return "nice";
},
int.parse("3"): () {
return "better";
},
});
T? whenDouble
Used to replace the [switch] method, because in some scenarios, an error warning of Case expressions must be constant;
If there is [value] in [Map.keys] of [conditionMap], execute its corresponding [ValueGetter] method
example:
String? status = whenDouble<String>(2.0, {
0.1: () {
return "good";
},
1.0 + 1: () {
return "nice";
},
double.parse("3.2"): () {
return "better";
},
});
T? whenBool
Used to replace the switch method, because some scenes use [switch] to cause an error warning of Case expressions must be constant.
If there is [value] in [Tuple2.item1] of [conditionList], execute its corresponding [ValueGetter] method
example:
double? degree = whenBool<double>(false, [
Tuple2(
"is Long String".length > 10,
() {
return 0.0;
},
),
Tuple2(
100 / 10 == 0,
() {
return 1.0;
},
),
Tuple2(
"apple".contains("a"),
() {
return 2.0;
},
),
]);
return degree;
T? whenValue
The super evolution version💖💖💖 of [switch] method, all basic types of values can be compared, including [List], [Map], [Set], and [Iterable].
All need do is [value] in [Map.keys] of [conditionMap], its corresponding [ValueGetter] method will be executed
example:
String? kind = whenValue<List, String>(
["apple", "orange"],
{
["cat", "dog"]: () {
return "pets";
},
["apple", "orange"]: () {
return "fruits";
},
["red", "white", "black"]: () {
return "colors";
},
},
);
T? when
The when function of the Kotlin version of the method [switch].
As long as the first true is found in [Map.keys] of [conditionMap], its corresponding [ValueGetter] method will be executed immediately and the relative value will be returned.
If it is not found, it will return null; if you need a default value, you can add a MapEntry with a key equal to true at the end of the Map
example:
String? winner = when<String>({
"Dart is Language".contains("UI"): () {
return "Flutter";
},
"Flutter is UI Framework".contains("UI"): () {
return "Flutter";
},
});
T? whenTrue
The when function of the Kotlin version of the method [switch]，its conditional expression will be calculated。.
As long as [conditionMap] to [Map.keys] appears first execution result is true, it will immediately perform corresponding [ValueGetter] method, and an opposite return value.
If it is not found, it will return null; if you need a default value, you can add a MapEntry with a key equal to true at the end of the Map
example:
String? something = whenTrue<String>({
() {
if (1 + 100 * 1000 < 2000) {
return false;
} else if ("Who is my lovely baby?".length > 10) {
return true;
} else {
return false;
}
}: () {
return "Test OK";
},
() {
return int.tryParse("3.14*") != null;
}: () {
return "PI get";
}
});
Example Demo:
testWhenValue() {
String? kind = whenValue<List, String>(
["apple", "orange"],
{
["cat", "dog"]: () {
return "pets";
},
["apple", "orange"]: () {
return "fruits";
},
["red", "white", "black"]: () {
return "colors";
},
},
);
return kind;
}
testWhenString() {
int howManyFruits = 2;
int? index = whenString<int>("banana🍌", {
"water" + "melon".more(): () {
return 1;
},
"apple".more(): () {
return 2;
},
howManyFruits <= 1 ? "orange" : "oranges": () {
return 3;
},
"banana" + "🍌": () {
return 4;
},
"grape": () {
return 5;
},
});
return index;
}
testWhen() {
String? winner = when<String>({
"Dart is Language".contains("UI"): () {
return "Flutter";
},
"Flutter is UI Framework".contains("UI"): () {
return "Flutter";
},
});
return winner;
}
testWhenDoubleSafe() {
String status = whenDoubleSafe<String>(
2.1,
{
0.1: () {
return "good";
},
1.0 + 1: () {
return "nice";
},
double.parse("3.2"): () {
return "better";
},
},
defaultValue: () => "other",
);
expect(status, "other");
};
Demo Pictrue
