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Null aware operators in Dart
Posted on 7 Nov, 2021
Null aware operators makes handling real world data very intuitive & easy. Let's have a brief overview of all the 4 null aware operators in Dart.
The ?. operator
?. operatorPrevent method call on null objects
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// call func() only if myVar is not null
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myVar?.func();
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// can also be chained
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final value = myVar?.getValue()?.valueA;
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This is similar to following code
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myVar = myVar == null ? null : myVar.func();
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The ?? operator
?? operatorThis operator can be used to assign a default fallback value.
Return the first expression IFF it is not null.
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// if unkownSource is null assign username with "default value" otherwise assign the value of unkownSource
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username = unkownSource ?? "default value";
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The ??= operator
??= operatorAssign a value IFF it is not null.
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// assign string "test" to myVar only if myVar is null
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myVar ??= "test";
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The ...? operator - Null aware spread operator
...? operator - Null aware spread operatorExpand list elements IFF it's not null
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void main() {
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List<int> varA = [2, 3, 4];
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List<int>? varB = null;
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final concatList = [1, ...varA, ...?varB];
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print(concatList);
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// [1, 2, 3, 4]
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}
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