Object references

Preserve reference (preventing circular reference stackoverflow)

When mapping objects with circular references, a stackoverflow exception will result. This is because Mapster will get stuck in a loop trying to recursively map the circular reference. If you would like to map circular references or preserve references (such as 2 properties pointing to the same object), you can do it by setting PreserveReference to true

TypeAdapterConfig<TSource, TDestination>
    .NewConfig()
    .PreserveReference(true);

NOTE: Projection doesn't support circular reference. To overcome, you might use Adapt instead of ProjectToType.

TypeAdaptConfig.GlobalSettings.Default.PreserveReference(true);
var students = context.Student.Include(p => p.Schools).Adapt<List<StudentDTO>>();

NOTE: in Mapster setting is per type pair, not per hierarchy (see https://github.com/chaowlert/Mapster/wiki/Nested-class-mapping). Therefore, you need to apply config to all type pairs.

TypeAdapterConfig<ParentPoco, ParentDto>.NewConfig().PreserveReference(true);
TypeAdapterConfig<ChildPoco, ChildDto>.NewConfig().PreserveReference(true);
TypeAdapterConfig<GrandChildPoco, GrandChildDto>.NewConfig().PreserveReference(true);

Or you can set PreserveReference in global setting.

TypeAdapterConfig.GlobalSettings.Default.PreserveReference(true);

If you don't want to set config in global setting, you can also use Fork.

var forked = TypeAdapterConfig.GlobalSettings.Default.Fork(config => config.Default.PreserveReference(true));
var parentDto = parentPoco.Adapt<ParentDto>(forked);

Shallow copy

By default, Mapster will recursively map nested objects. You can do shallow copying by setting ShallowCopyForSameType to true.

TypeAdapterConfig<TSource, TDestination>
    .NewConfig()
    .ShallowCopyForSameType(true);

Mapping very large objects

For performance optimization, Mapster tried to inline class mapping. This process will takes time if your models are complex.

You can skip inlining process by:

TypeAdapterConfig.GlobalSettings.Default
    .AvoidInlineMapping(true);