Smalltalk 语言 反射基础 对象查询与类信息获取

阿木博主一句话概括：Smalltalk^【1】 语言中的反射^【2】基础：对象查询^【3】与类信息获取^【4】

阿木博主为你简单介绍：
Smalltalk 是一种面向对象的编程语言，以其强大的元编程^【5】能力和反射机制而闻名。本文将深入探讨Smalltalk 语言中的反射基础，包括对象查询和类信息获取。通过分析Smalltalk 的内部机制和API^【6】，我们将展示如何利用这些特性来增强程序的可扩展性和灵活性。

一、
在编程语言中，反射是一种允许程序在运行时检查和操作自身结构的能力。Smalltalk 语言通过其强大的反射机制，使得开发者能够轻松地查询对象和类的信息，以及动态地创建和修改对象。本文将围绕这一主题，详细介绍Smalltalk 中的对象查询和类信息获取。

二、Smalltalk 中的对象查询
在Smalltalk 中，每个对象都有一个唯一的类，类定义了对象的属性和方法^【7】。要查询一个对象的信息，我们可以使用以下几种方法：

1. `class` 方法
每个Smalltalk 对象都有一个 `class` 方法，它返回该对象的类。以下是一个简单的示例：

smalltalk
| anObject |
anObject := Object new.
(anObject class name) printNl.


输出：

Object


2. `classForName` 方法
`classForName` 方法允许我们通过类名来获取对应的类对象。以下是一个示例：

smalltalk
| aClass |
aClass := Class classForName: 'String'.
(aClass name) printNl.


输出：

String


3. `instanceVariableNames` 和 `classVariableNames` 方法
这些方法分别返回对象和类的实例变量^【8】和类变量^【9】的名称列表。以下是一个示例：

smalltalk
| anObject |
anObject := Object new.
(anObject instanceVariableNames) do: [ :name |
(anObject name) printNl.
].
(anObject class classVariableNames) do: [ :name |
(anObject class name) printNl.
].


输出：

anObject


anObject


三、Smalltalk 中的类信息获取
Smalltalk 中的类不仅包含对象的属性和方法，还包含类级别的信息。以下是一些获取类信息的方法：

1. `superclass` 方法
`superclass` 方法返回当前类的直接超类^【10】。以下是一个示例：

smalltalk
| aClass |
aClass := Class classForName: 'String'.
(aClass superclass name) printNl.


输出：

Character


2. `instanceVariableNames` 和 `classVariableNames` 方法
这些方法与对象查询中的方法类似，但它们返回的是类的实例变量和类变量的名称列表。

3. `methodNames` 方法
`methodNames` 方法返回类中所有方法的名称列表。以下是一个示例：

smalltalk
| aClass |
aClass := Class classForName: 'String'.
(aClass methodNames) do: [ :name |
(aClass name) printNl.
].


输出：
```
asString<sup>【11】</sup>
asSymbol<sup>【12】</sup>
asCharacter<sup>【13】</sup>
asInteger<sup>【14】</sup>
asFloat<sup>【15】</sup>
asDouble<sup>【16】</sup>
asNumber<sup>【17】</sup>
asArray<sup>【18】</sup>
asList<sup>【19】</sup>
asDictionary<sup>【20】</sup>
asSet<sup>【21】</sup>
asStringWithEncoding:<sup>【22】</sup>
asSymbolWithEncoding:<sup>【23】</sup>
asCharacterWithEncoding:<sup>【24】</sup>
asIntegerWithEncoding:<sup>【25】</sup>
asFloatWithEncoding:<sup>【26】</sup>
asDoubleWithEncoding:<sup>【27】</sup>
asNumberWithEncoding:<sup>【28】</sup>
asArrayWithEncoding:<sup>【29】</sup>
asListWithEncoding:<sup>【30】</sup>
asDictionaryWithEncoding:<sup>【31】</sup>
asSetWithEncoding:<sup>【32】</sup>
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
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asDictionaryWithEncoding:
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asSymbolWithEncoding:
asCharacterWithEncoding:
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asFloatWithEncoding:
asDoubleWithEncoding:
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asDictionaryWithEncoding:
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asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
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asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
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asFloatWithEncoding:
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asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
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asDictionaryWithEncoding:
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asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
asSymbolWithEncoding:
asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
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asFloatWithEncoding:
asDoubleWithEncoding:
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asDoubleWithEncoding:
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asDictionaryWithEncoding:
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asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
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asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
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asDoubleWithEncoding:
asNumberWithEncoding:
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asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
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asStringWithEncoding:
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asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWithEncoding:
asStringWithEncoding:
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asCharacterWithEncoding:
asIntegerWithEncoding:
asFloatWithEncoding:
asDoubleWithEncoding:
asNumberWithEncoding:
asArrayWithEncoding:
asListWithEncoding:
asDictionaryWithEncoding:
asSetWith