Write<A> abstract mixin

abstract mixin class Write<A>

Describes how to encode a value of type A into SQL parameter slots. A Write may occupy multiple parameter positions.

Implementers

• ReadWrite<A>

Available Extensions

• WriteOptionOps<A>

Constructors

Write()

Write()

Properties

hashCode no setter inherited

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation

external int get hashCode;

length no setter

int get length

The number of parameter slots occupied by this Write.

Implementation

int get length => puts.length;

puts no setter

IList<Put<dynamic>> get puts

The individual column Put encoders that make up this Write.

Implementation

IList<Put<dynamic>> get puts;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

Methods

contramap()

Write<B> contramap<B>(A Function(B) f)

Adapts this Write to accept a different type B by applying f before encoding.

Implementation

Write<B> contramap<B>(Function1<B, A> f) => Write.instance(
  puts,
  (params, n, value) => setParameter(params, n, f(value)),
);

encode()

StatementParameters encode(A value)

Encodes value to a StatementParameters.

Implementation

StatementParameters encode(A value) => setParameter(StatementParameters.empty(), 0, value);

noSuchMethod() inherited

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation

@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

setParameter()

StatementParameters setParameter(StatementParameters params, int n, A a)

Sets the parameter at position n in params to the encoded form of a, returning updated parameters.

Implementation

StatementParameters setParameter(StatementParameters params, int n, A a);

toString() inherited

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation

external String toString();

Extension Methods

optional() extension

Write<Option<A>> optional()

Returns a Write that encodes None as null and Some with the underlying encoder.

Available on Write<A>, provided by the WriteOptionOps<A> extension

Implementation

Write<Option<A>> optional() => Write.instance(
  puts,
  (params, n, a) => a.fold(
    () => params.setParameter(n + length - 1, null),
    (some) => setParameter(params, n, some),
  ),
);

Operators

operator ==() inherited

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

• Total: It must return a boolean for all arguments. It should never throw.

• Reflexive: For all objects o, o == o must be true.

• Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

• Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Object.

Implementation

external bool operator ==(Object other);

Static Properties

bigInt final

final Write<BigInt> bigInt

Encodes a BigInt parameter.

Implementation

static final Write<BigInt> bigInt = Write.fromPut(Put.bigInt);

blob final

final Write<ByteVector> blob

Encodes a binary blob.

Implementation

static final Write<ByteVector> blob = Write.fromPut(Put.blob);

boolean final

final Write<bool> boolean

Encodes a boolean parameter.

Implementation

static final Write<bool> boolean = Write.fromPut(Put.boolean);

dateTime final

final Write<DateTime> dateTime

Encodes a DateTime parameter.

Implementation

static final Write<DateTime> dateTime = Write.fromPut(Put.dateTime);

dubble final

final Write<double> dubble

Encodes a double parameter.

Implementation

static final Write<double> dubble = Write.fromPut(Put.dubble);

integer final

final Write<int> integer

Encodes an int parameter.

Implementation

static final Write<int> integer = Write.fromPut(Put.integer);

json final

final Write<Json> json

Encodes a Json value parameter.

Implementation

static final Write<Json> json = Write.fromPut(Put.json);

string final

final Write<String> string

Encodes a String parameter.

Implementation

static final Write<String> string = Write.fromPut(Put.string);

unit final

final Write<Unit> unit

A Write that occupies no parameter slots. Useful as an identity for composing writes.

Implementation

static final Write<Unit> unit = Write.instance(nil(), (params, _, _) => params);

Static Methods

fromPut()

Write<A> fromPut<A>(Put<A> put)

Creates a Write from a single-column Put.

Implementation

static Write<A> fromPut<A>(Put<A> put) => Write.instance(
  ilist([put]),
  (params, n, value) => put.setParameter(params, n, value),
);

instance()

Write<A> instance<A>(
  IList<Put<dynamic>> puts,
  StatementParameters Function(StatementParameters, int, A) f,
)

Creates a Write from a list of Put encoders and a function that sets parameter values in StatementParameters starting at index n.

Implementation

static Write<A> instance<A>(
  IList<Put<dynamic>> puts,
  Function3<StatementParameters, int, A, StatementParameters> f,
) => _WriteF(puts, f);