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| 1 | +from pydantic import BaseModel, Field, model_serializer |
| 2 | +from typing import Annotated |
| 3 | + |
| 4 | +from .mixin import BaseElement |
| 5 | + |
| 6 | + |
| 7 | +class PlaceholderName(BaseModel): |
| 8 | + """Represents a reference to a named element. |
| 9 | +
|
| 10 | + This placeholder is replaced with a physically distinct |
| 11 | + element during beamline expansion. |
| 12 | +
|
| 13 | + This class behaves like a string (via __str__ and __eq__) but stores |
| 14 | + a true reference to the actual element object once it's resolved. |
| 15 | +
|
| 16 | + The element field holds a reference (not a copy) to the actual element. |
| 17 | +
|
| 18 | + Attributes: |
| 19 | + name: The name of the referenced element |
| 20 | + element: A reference to the resolved element object (None until resolved) |
| 21 | +
|
| 22 | + Example: |
| 23 | + >>> ref = PlaceholderName(name="drift1") |
| 24 | + >>> ref.name |
| 25 | + 'drift1' |
| 26 | + >>> str(ref) |
| 27 | + 'drift1' |
| 28 | + >>> ref == "drift1" |
| 29 | + True |
| 30 | + >>> ref.element # None until resolved |
| 31 | + >>> drift = pals.Drift(name="drift1", length=1.0) |
| 32 | + >>> ref.element = drift |
| 33 | + >>> ref.is_resolved() |
| 34 | + True |
| 35 | + >>> ref.element is drift # True - it's a reference, not a copy |
| 36 | + True |
| 37 | + """ |
| 38 | + |
| 39 | + name: str = Field(..., description="The name of the referenced element") |
| 40 | + element: Annotated[ |
| 41 | + "BaseElement | None", |
| 42 | + Field(default=None, description="Reference to the resolved element object"), |
| 43 | + ] = None |
| 44 | + |
| 45 | + @model_serializer(mode="plain") |
| 46 | + def _serialize_as_name(self) -> str: |
| 47 | + """Serialize this reference as just its name. |
| 48 | +
|
| 49 | + This makes `model_dump()` return a string (the element name), so nested |
| 50 | + serialization (e.g. inside BeamLine.line) produces plain strings too. |
| 51 | + """ |
| 52 | + return self.name |
| 53 | + |
| 54 | + def __init__(self, name: str | None = None, /, **data): |
| 55 | + """Initialize with either positional name or keyword arguments.""" |
| 56 | + if name is not None: |
| 57 | + super().__init__(name=name, **data) |
| 58 | + else: |
| 59 | + super().__init__(**data) |
| 60 | + |
| 61 | + def __str__(self) -> str: |
| 62 | + """Return the element name as string.""" |
| 63 | + return self.name |
| 64 | + |
| 65 | + def __eq__(self, other: object) -> bool: |
| 66 | + """Enable string comparison.""" |
| 67 | + if isinstance(other, str): |
| 68 | + return self.name == other |
| 69 | + if isinstance(other, PlaceholderName): |
| 70 | + return self.name == other.name and self.element is other.element |
| 71 | + return False |
| 72 | + |
| 73 | + def __hash__(self) -> int: |
| 74 | + """Make hashable like a string.""" |
| 75 | + return hash(self.name) |
| 76 | + |
| 77 | + def is_resolved(self) -> bool: |
| 78 | + """Check if this reference has been resolved to an actual element.""" |
| 79 | + return self.element is not None |
| 80 | + |
| 81 | + def __repr__(self) -> str: |
| 82 | + """Return a representation of the PlaceholderName.""" |
| 83 | + resolved = "resolved" if self.is_resolved() else "unresolved" |
| 84 | + return f"PlaceholderName('{self.name}', {resolved})" |
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