DDD, how do you change a ValueObject?
The question refers to a situation in which you have to update/delete a valueobject.
Consider this situation.
You have an Order and you have Products and Products have ProductItems. Where ProductItem is a ValueObject. If you would have to update the list of productItems in Product (let's say update the quantity), how would you do it? How will you identify the exact ProductItem that requires the update ?
This is from the perspective or an OrderingContext, there should be a backing context where you have ProductItem stock and ProductItem pricing (InventoryContext), context where a ProductItem is more then just a ValueObject, but since we are under the OrderingContext, how would you update a ProductItem if you don't have a way to identify it?
architecture domain-driven-design software-design value-objects
asked Nov 20 '18 at 10:43
MCRMCR
594219
add a comment |
The question refers to a situation in which you have to update/delete a valueobject.
Consider this situation.
You have an Order and you have Products and Products have ProductItems. Where ProductItem is a ValueObject. If you would have to update the list of productItems in Product (let's say update the quantity), how would you do it? How will you identify the exact ProductItem that requires the update ?
This is from the perspective or an OrderingContext, there should be a backing context where you have ProductItem stock and ProductItem pricing (InventoryContext), context where a ProductItem is more then just a ValueObject, but since we are under the OrderingContext, how would you update a ProductItem if you don't have a way to identify it?
architecture domain-driven-design software-design value-objects
asked Nov 20 '18 at 10:43
MCRMCR
594219
What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have aMoneyvalue object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)
– Tseng
Nov 20 '18 at 10:55
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
product.ProductItem = new ProductItem(5, "Some Description");) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context
– Tseng
Nov 20 '18 at 11:13
2
As for how to identify it? You search for an ProductItem which as quantity5andSome Descriptionas description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id
– Tseng
Nov 20 '18 at 11:14
add a comment |
The question refers to a situation in which you have to update/delete a valueobject.
Consider this situation.
You have an Order and you have Products and Products have ProductItems. Where ProductItem is a ValueObject. If you would have to update the list of productItems in Product (let's say update the quantity), how would you do it? How will you identify the exact ProductItem that requires the update ?
This is from the perspective or an OrderingContext, there should be a backing context where you have ProductItem stock and ProductItem pricing (InventoryContext), context where a ProductItem is more then just a ValueObject, but since we are under the OrderingContext, how would you update a ProductItem if you don't have a way to identify it?
architecture domain-driven-design software-design value-objects
asked Nov 20 '18 at 10:43
MCRMCR
594219
The question refers to a situation in which you have to update/delete a valueobject.
Consider this situation.
You have an Order and you have Products and Products have ProductItems. Where ProductItem is a ValueObject. If you would have to update the list of productItems in Product (let's say update the quantity), how would you do it? How will you identify the exact ProductItem that requires the update ?
This is from the perspective or an OrderingContext, there should be a backing context where you have ProductItem stock and ProductItem pricing (InventoryContext), context where a ProductItem is more then just a ValueObject, but since we are under the OrderingContext, how would you update a ProductItem if you don't have a way to identify it?
architecture domain-driven-design software-design value-objects
architecture domain-driven-design software-design value-objects
asked Nov 20 '18 at 10:43
MCRMCR
594219
asked Nov 20 '18 at 10:43
MCRMCR
594219
asked Nov 20 '18 at 10:43
MCRMCR
594219
asked Nov 20 '18 at 10:43
MCRMCR
594219
asked Nov 20 '18 at 10:43
MCRMCR
594219
594219
What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have aMoneyvalue object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)
– Tseng
Nov 20 '18 at 10:55
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
product.ProductItem = new ProductItem(5, "Some Description");) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context
– Tseng
Nov 20 '18 at 11:13
2
As for how to identify it? You search for an ProductItem which as quantity5andSome Descriptionas description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id
– Tseng
Nov 20 '18 at 11:14
add a comment |
What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have aMoneyvalue object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)
– Tseng
Nov 20 '18 at 10:55
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
product.ProductItem = new ProductItem(5, "Some Description");) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context
– Tseng
Nov 20 '18 at 11:13
2
As for how to identify it? You search for an ProductItem which as quantity5andSome Descriptionas description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id
– Tseng
Nov 20 '18 at 11:14
What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have a
Money value object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)– Tseng
Nov 20 '18 at 10:55
What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have a
Money value object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)– Tseng
Nov 20 '18 at 10:55
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
product.ProductItem = new ProductItem(5, "Some Description") ;) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context– Tseng
Nov 20 '18 at 11:13
product.ProductItem = new ProductItem(5, "Some Description") ;) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context– Tseng
Nov 20 '18 at 11:13
2
2
As for how to identify it? You search for an ProductItem which as quantity
5 and Some Description as description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id– Tseng
Nov 20 '18 at 11:14
As for how to identify it? You search for an ProductItem which as quantity
5 and Some Description as description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id– Tseng
Nov 20 '18 at 11:14
add a comment |
1 Answer
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You identify the Value object in a list by whatever means you need, there is not rule regarding that.
For example, in this case, one way to identify it is to use it's numeric index from the list. If you need something more stable (i.e. that works also in case of items reordering) you can have GUIDs instead of numeric indexes, in languages that support this. For example, PHP lets you use strings for array access and GUIDs can be converted to strings before use in an array lookup.
The important rule to remember about Value objects: they should be immutable, that is, if you need to update one then you replace it with another instance.
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
add a comment |
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You identify the Value object in a list by whatever means you need, there is not rule regarding that.
For example, in this case, one way to identify it is to use it's numeric index from the list. If you need something more stable (i.e. that works also in case of items reordering) you can have GUIDs instead of numeric indexes, in languages that support this. For example, PHP lets you use strings for array access and GUIDs can be converted to strings before use in an array lookup.
The important rule to remember about Value objects: they should be immutable, that is, if you need to update one then you replace it with another instance.
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
add a comment |
You identify the Value object in a list by whatever means you need, there is not rule regarding that.
For example, in this case, one way to identify it is to use it's numeric index from the list. If you need something more stable (i.e. that works also in case of items reordering) you can have GUIDs instead of numeric indexes, in languages that support this. For example, PHP lets you use strings for array access and GUIDs can be converted to strings before use in an array lookup.
The important rule to remember about Value objects: they should be immutable, that is, if you need to update one then you replace it with another instance.
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
add a comment |
You identify the Value object in a list by whatever means you need, there is not rule regarding that.
For example, in this case, one way to identify it is to use it's numeric index from the list. If you need something more stable (i.e. that works also in case of items reordering) you can have GUIDs instead of numeric indexes, in languages that support this. For example, PHP lets you use strings for array access and GUIDs can be converted to strings before use in an array lookup.
The important rule to remember about Value objects: they should be immutable, that is, if you need to update one then you replace it with another instance.
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
You identify the Value object in a list by whatever means you need, there is not rule regarding that.
For example, in this case, one way to identify it is to use it's numeric index from the list. If you need something more stable (i.e. that works also in case of items reordering) you can have GUIDs instead of numeric indexes, in languages that support this. For example, PHP lets you use strings for array access and GUIDs can be converted to strings before use in an array lookup.
The important rule to remember about Value objects: they should be immutable, that is, if you need to update one then you replace it with another instance.
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
answered Nov 20 '18 at 12:36
Constantin GalbenuConstantin Galbenu
11.1k21531
11.1k21531
add a comment |
add a comment |
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What is a ProductItem? Value Objects by their very nature are identified by their value (D'oh). If you have a
Moneyvalue object, then it's identified by "Amount" (i.e. a decimal value) and "Currency" (either another value type or a string)– Tseng
Nov 20 '18 at 10:55
@Tseng: a ProductItem is something that has a name and a quantity. So assuming you want to update the quantity, how would you do it ? I'm guessing you identify it by its ProductId and the name ?
– MCR
Nov 20 '18 at 11:07
product.ProductItem = new ProductItem(5, "Some Description");) That's the very nature of it. On a collection, you first need to remove it then add a new, value type to it. Also generally you seem to have a bad understanding of DDD. Are Orders and Products really a different bounded context? If yes, you don't change one of it from the other context. A bounded context never directly acts on another BC's aggregates. You always have to use some kind of anti-corruption layer to transfer that to a message and that back into the other bounded context– Tseng
Nov 20 '18 at 11:13
2
As for how to identify it? You search for an ProductItem which as quantity
5andSome Descriptionas description. Thats how value objects are identified, by the SUM of their properties unlike entities which are identified by an unique id– Tseng
Nov 20 '18 at 11:14