/ doc / toc / ARCCore / Enum / ARConcepts / PropertyAccess / __TOCDet / Attribute

Attribute

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Description = The general mechanism for accessing properties of objects in AgoRapide.0x000D0x000A0x000D0x000AImplemented through the -IP- (IProperty) interface mechanism.0x000D0x000A0x000D0x000AIn applications with lot of different data fields it might be difficult to 1) Specify from the beginning exactly which fields you need, 2) To decide if they are actually available at the stage of processing, 3) To explain them in logs and debug-messages and 4) To implement storage for them.0x000D0x000A0x000D0x000AThis can lead to a messy bug-prone implementation because you have to make assumptions about the data available, or you just leave out desired functionality because of a constant need for generating boilerplate code just to accomplish what is really a trivial task that should be inbuilt / automated somehow from the beginning.TODO: CLARIFY SENTENCE ABOVE.0x000D0x000A0x000D0x000AAgoRapide uses a standardized generic mechanism for accessing properties of objects. It is implemented through the -IP- (IProperty) interface mechanism0x000D0x000A0x000D0x000AThis means that for every field / property you have concepts like the following ready for use:0x000D0x000A0x000D0x000A1) Both Get and TryGet are always available. Get will throw a detailed exception if not successful (see default interface methods in -IP- like -TryGetV-)0x000D0x000A0x000D0x000A2) Get has the choice of a default value to return if not successful (instead of throwing an exception) (see default interface methods in -IP- like -GetV-).0x000D0x000A0x000D0x000A3) Meta-information for a property, like who created it or how old it is (see -PP- like -Cid- and -Created-).0x000D0x000A0x000D0x000A4) Defining cardinality like single, multiple and so on (with corresponding validation and parsing) (see -Cardinality-).0x000D0x000A0x000D0x000A5) Whether the field is obligatory or not (see -IsObligatory-).0x000D0x000A0x000D0x000A6) Default value (see -DefaultValue-).0x000D0x000A0x000D0x000A7) Guard against multiple setting of same property (see -SetP- versus -AddP-, the latter throws a -KeyAlreadyExistsException- for multiple attempts to set a property) 0x000D0x000ATODO: Regarding 7), introduce in PKTypeAttribute a setting for this (SetOnlyOnceAllowed or similar)0x000D0x000ATODO: but remember that must then be honoured by all implementations of -AddP- and0x000D0x000ATODO: you must also think through implications when updating object from the property stream0x000D0x000A0x000D0x000AAt the entity level (-IP--level), you get the following:0x000D0x000A1) Automatic assertion of integrity (assertion that -IsObligatory- values are set for instance, see -AssertIntegrity-).0x000D0x000A0x000D0x000A2) An automatic ToString() method for your objects (not even with boilerplate auto-generated code but all automatically from within the framework itself).0x000D0x000ATODO: Actually not implemented as of May 2020, but 'easily done'.0x000D0x000A0x000D0x000A3) A truly 'deep' copy is always possible (see -DeepCopy-).0x000D0x000A0x000D0x000A4) Changes are automatically logged (see -app- and -ExposingApplicationState-).0x000D0x000A0x000D0x000ASee also -ITypeDescriber- which extends the idea of a standardized parsing and validation mechanism to single property-values also
EnumMember = PropertyAccess
EnumType = ARConcepts
LongDescription = FAQ: How does the -PropertyAccess- mechanism work with inheritance?0x000D0x000AClasses can of course have inheritance but accessing the properties may be a little non-intuitive.0x000D0x000AFor instance, for -ClassAttribute-, the property -Description- from the base type -BaseAttribute- is also present. Unfortunately you get little help from tools like Intellisense in Visual Studio to remember this (unless you implement -BoilerplateCodeProperties-).0x000D0x000AHowever, all the information is contained within -TaggingOfPropertyKeys- so -ARCAPI- for instance (with help from -ARCQuery-) can communicate the relationships clearly to the outside, for instance expressed in Graph QL SDL.0x000D0x000A0x000D0x000AIn general this way of storing properties incidentally also helps with issues like0x000D0x000A0x000D0x000A1) Enabling the AgoRapide concept of -PropertyStream- like serialization (see -ToPropertyStream- and0x000D0x000Adeserialization (see -TryParse-),0x000D0x000A0x000D0x000A2) -TaggingOfPropertyKeys-,0x000D0x000A0x000D0x000Aetc. etc..0x000D0x000A0x000D0x000ASome drawbacks of this mechanism are of course:0x000D0x000A0x000D0x000A1) The risk of increased memory usage. See -MemoryConsumption- for more details about this.0x000D0x000A0x000D0x000A2) Convoluted syntax when accessing properties.0x000D0x000AThis can be alleviated by implementing traditional setters / getters, using the standardized property access mechanism 'behind the scene'.0x000D0x000A0x000D0x000A3) Less static strong typing than what is default in C# (see for instance -AssertTypeIntegrity-).0x000D0x000A0x000D0x000AAll these drawbacks, 1), 2) and 3) can be alleviated by using traditional setters / getters, and also traditional storage. See -ARCDoc- for practical examples of this, especially classes -Demonstrator-, -Apple-, -Orange- and -Banana-.0x000D0x000A0x000D0x000ASee also -BoilerplateCodeProperties- and -BoilerplateCodePropertiesAndStorage-.0x000D0x000A

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