我正在编写一个Clojure宏，它接受使用java.awt.GridBagLayout的面板描述，并在编译时生成等效代码（使用(doto ...)）。我知道seesaw，但我正在努力学习宏观写作的细节。
我的问题：
(Insets. 5 5 5 5)）（生成字节码）？(eval ...)或#=(...)，因为没有关联的运行时惩罚？我知道这可以写成(defn ...)并且（轻松）解决问题。我想用宏实现相同的结果，因为我可以看到其他情况，其中函数的运行时性能损失可能是不可接受的（在这种情况下不，因为这是GUI代码）。我写这个宏的原因是因为我相信结果比手动扩展版本更容易阅读和维护。
我已经包含了两个(print-dup...)多方法的定义以努力满足编译器并消除（不成功）运行时错误消息“无法在代码中嵌入对象，可能没有定义print-dup：java .awt.Insets [顶= 5，左= 5，底部= 5，右侧= 5]“
宏的调用如下：
(grid-bag-container (JPanel. (GridBagLayout.))
[(JButton "Monday") :gridwidth 2 :weightx 1.0 :fill :HORIZONTAL]
[(JCheckBox "Vacation")]
[[(JLabel. "Arrive:")] [(JTextField. 6) :fill :HORIZONTAL]]
[[(JLabel. "Depart:")] [(JTextField. 6) :fill :HORIZONTAL]])
这是预期的扩展（漂亮的打印，易于阅读： - ））：
(doto (JPanel. (GridBagLayout.))
(.add (JButton "Monday")
(GridBagConstraints. 0 0 2 1 1.0 0
(. GridBagConstraints WEST)
(. GridBagConstraints HORIZONTAL)
(Insets. 2 2 2 2) 0 0))
(.add (JCheckBox "Vacation")
(GridBagConstraints. 0 1 1 1 0 0
(. GridBagConstraints WEST)
(. GridBagConstraints NONE)
(Insets. 2 2 2 2) 0 0))
(.add (JLabel. "Arrive:")
(GridBagConstraints. 0 2 1 1 0 0
(. GridBagConstraints WEST)
(. GridBagConstraints NONE)
(Insets. 2 2 2 2) 0 0))
(.add (JTextField. 6)
(GridBagConstraints. 1 2 1 1 0 0
(. GridBagConstraints WEST)
(. GridBagConstraints HORIZONTAL)
(Insets. 2 2 2 2) 0 0))
(.add (JLabel. "Depart:")
(GridBagConstraints. 0 3 1 1 0 0
(. GridBagConstraints WEST)
(. GridBagConstraints NONE)
(Insets. 2 2 2 2) 0 0))
(.add (JTextField. 6)
(GridBagConstraints. 1 3 1 1 0 0
(. GridBagConstraints WEST)
(. GridBagConstraints HORIZONTAL)
(Insets. 2 2 2 2) 0 0)))
以下是代码：
(defmethod print-dup java.awt.GridBagConstraints [args writer]
"A multimethod for converting java.awt.GridBagConstraints to a compiled form.
@param args a collection of constructor arguments
@param writer the Writer to which the output should be generated"
(.write writer "#=(java.awt.GridBagConstraints. ")
(.write writer (apply str (interpose " " (map str args))))
(.write writer ")"))
(defmethod print-dup java.awt.Insets [args writer]
"A multimethod for converting java.awt.Insets to a compiled form.
@param args a collection of (Integer) constructor arguments
@param writer the Writer to which the output should be generated"
(.write writer "#=(java.awt.Insets. ")
(.write writer (apply str (interpose " " (map str args))))
(.write writer ")"))
(defmacro grid-bag-container [container & args]
"Fill a container having a GridBagLayout with the given components.
The args can start with an optional default-constraints map (see the
doc-string for build-gbc (below) for details on the constraints map).
Following the optional default-constraints are zero or more rows.
Each row is a vector containing either a single component specification
or multiple vectors of component specifications. Each component specification
is a component (e.g.: JButton) followed by one or more key-value constraints
of the same form as the default-constraints. Note that these key-value
pairs are NOT contained in a map. Each row vector will be placed in
the next gridy position (starting with 0). If a row vector contains only
one component specification, that component will be placed at gridx=0.
If a row vector contains vectors, each will be placed at the next gridx
position (starting with 0). The default values for the constraints are as
follows:
:gridwidth 1
:gridheight 1
:weightx 0
:weighty 0
:anchor :WEST
:fill :NONE
:insets (Insets. 5 5 5 5)
:ipadx 0
:ipady 0
For example:
(grid-bag-container
(JPanel.)
{:insets (Insets. 2 2 2 2)} ; Override the default (Insets. 5 5 5 5)
[button :gridwidth 2 :weightx 1] ; Add a button at (gridx=0, gridy=0) with the
; gridwidth=2 (overriding the default 1),
; and weightx=1 (overriding the default 0)
[[label] [textfield :fill :HORIZONTAL]]) ; Add a label at (gridx=0, gridy=1)
; and a textfield at (gridx=1, gridy=1),
; with fill=GridBagContraints.CENTER
; (overriding the default GridBagContraints.WEST)
This example will expand to
(doto container
(.add button (build-gbc {:gridx 0 :gridwidth 2 :ipadx 0 :ipady 0 :anchor :WEST :weighty 0
:gridheight 1 :weightx 1 :fill :NONE :insets (Insets. 2 2 2 2)
:gridy 0}))
(.add label (build-gbc {:gridx 0 :gridwidth 1 :ipadx 0 :ipady 0 :anchor :WEST :weighty 0
:gridheight 1 :weightx 0 :fill :NONE :insets (Insets. 2 2 2 2)
:gridy 1}))
(.add textfield (build-gbc {:gridx 1 :gridwidth 1 :ipadx 0 :ipady 0 :anchor :WEST :weighty 0
:gridheight 1 :weightx 0 :fill :HORIZONTAL :insets (Insets. 2 2 2 2)
:gridy 1})))
@param container the java.awt.Container to fill
@args an optional default-constraints map followed by zero or more row specifications
@returns the container
build-gbc:
Build and return a GridBagConstraints containing the given constraints map.
Each constraint is a (:key value) pair where the name of the key is a
GridBagConstraints field (e.g.: gridwidth) and the value is either a keyword
(e.g.: :CENTER), in which case the GridBagConstraints constant of the same name
(e.g.: GridBagConstraints.CENTER) is used, or anything else, in which case the
corresponding field is set to that value.
Example:
(build-gbc {:gridx 0
:gridy 0
:gridheight 1
:gridwidth 2
:weightx 1
:weighty 0
:anchor :CENTER
:fill :NONE
:insets (Insets. 2 2 2 2)
:ipadx 0
:ipady 0})
will build and return a GridBagConstraints containing the following field values:
gridx 0
gridy 0
gridheight 1
gridwidth 2
weightx 1
weighty 0
anchor GridBagConstraints.CENTER
fill GridBagConstraints.NONE
insets (Insets. 2 2 2 2)
ipadx 0
ipady 0.
@param constraints a map containing the GridBagConstraints constraint values
@returns a new GridBagConstraints
@see http://stuartsierra.com/2010/01/05/taming-the-gridbaglayout"
(let [global-defaults {:gridwidth 1
:gridheight 1
:weightx 0
:weighty 0
:anchor :WEST
:fill :NONE
:insets (Insets. 5 5 5 5)
:ipadx 0
:ipady 0}
defaults
(if (map? (first args))
(first args)
{})
args
(into []
(if (map? (first args))
(rest args)
args))
build-gbc
(fn [constraints]
(let [process-value
#(if (nil? %)
nil
(if (keyword? %)
`(. GridBagConstraints ~(symbol (name %)))
%))]
`(GridBagConstraints.
~(process-value (:gridx constraints))
~(process-value (:gridy constraints))
~(process-value (:gridwidth constraints))
~(process-value (:gridheight constraints))
~(process-value (:weightx constraints))
~(process-value (:weighty constraints))
~(process-value (:anchor constraints))
~(process-value (:fill constraints))
~(process-value (:insets constraints))
~(process-value (:ipadx constraints))
~(process-value (:ipady constraints)))))]
`(doto ~container
~@(loop [end (count args)
gridy 0
ret []]
(if (= end gridy)
ret
(let [row (nth args gridy)
process-item
(fn [component gridx gridy constraints]
(let [constraints
(reduce into global-defaults
[{:gridx gridx :gridy gridy}
defaults
(vec (map vec (partition 2 constraints)))])]
`(.add ~component ~(build-gbc constraints))))]
(if (vector? (first row))
(recur end
(inc gridy)
(into ret (for [gridx (range (count row))
:let [item (nth row gridx)
component (first item)
constraints (rest item)]]
(process-item component gridx gridy constraints))))
(recur end
(inc gridy)
(conj ret (let [component (first row)
constraints (rest row)]
(process-item component 0 gridy constraints)))))))))))
答案 0 :(得分：4)
AFAICS，您遇到的问题是您在宏中生成Inset对象，而不是代码来生成Inset对象。 IOW，全局默认值中的:insets (Insets. 5 5 5 5)应该是:insets '(Insets. 5 5 5 5)或类似内容。
print-dup代码令人困惑且不需要，所以请将其删除。