mirror of https://github.com/AMT-Cheif/drift.git
Add substrExpr to query builder
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@ -137,10 +137,31 @@ extension StringExpressionOperators on Expression<String> {
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/// and [length] can be negative to return a section of the string before
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/// [start].
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Expression<String> substr(int start, [int? length]) {
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return substrExpr(
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Constant(start), length != null ? Constant(length) : null);
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}
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/// Calls the [`substr`](https://sqlite.org/lang_corefunc.html#substr)
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/// function with arbitrary expressions as arguments.
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///
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/// For instance, this call uses [substrExpr] to remove the last 5 characters
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/// from a column. As this depends on its [StringExpressionOperators.length],
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/// it needs to use expressions:
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///
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/// ```dart
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/// update(table).write(TableCompanion.custom(
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/// column: column.substrExpr(Variable(1), column.length - Variable(5))
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/// ));
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/// ```
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///
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/// When both [start] and [length] are Dart values (e.g. [Variable]s or
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/// [Constant]s), consider using [substr] instead.
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Expression<String> substrExpr(Expression<int> start,
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[Expression<int>? length]) {
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return FunctionCallExpression('SUBSTR', [
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this,
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Constant<int>(start),
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if (length != null) Constant<int>(length),
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start,
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if (length != null) length,
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]);
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}
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}
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@ -125,7 +125,11 @@ void main() {
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});
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test('substring', () {
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expect(eval(Constant('hello world').substr(7)), completion('world'));
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final input = Constant('hello world');
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expect(eval(input.substr(7)), completion('world'));
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expect(eval(input.substrExpr(Variable(1), input.length - Variable(6))),
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completion('hello'));
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});
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});
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@ -52,5 +52,8 @@ void main() {
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test('substr', () {
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expect(expression.substr(10), generates('SUBSTR(col, 10)'));
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expect(expression.substr(10, 2), generates('SUBSTR(col, 10, 2)'));
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expect(expression.substrExpr(Variable(1), expression.length - Variable(5)),
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generates('SUBSTR(col, ?, LENGTH(col) - ?)', [1, 5]));
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});
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}
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