What Is a Handle?

Certain kinds of MATLAB^®对象是处理。当变量固定句柄时，它实际上保留对对象的引用。

Handle objects enable more than one variable to refer to the same object. Handle-object behavior affects what happens when you copy handle objects and when you pass them to functions.

Copies of Handles

句柄对象变量的所有副本都涉及相同的基础对象。这种参考行为意味着如果hidentifies a handle object, then,

H2 = H;

Creates another variable,h2，指的是与h。

例如，MATLABaudioplayer功能creates a handle object that contains the audio source data to reproduce a specific sound segment. The variable returned by theaudioplayer函数可以标识音频数据，并使您能够访问对象功能播放音频。

MATLAB software includes audio data that you can load and use to create anaudioplayerobject. This sample load audio data, creates the audio player, and plays the audio:

loadgongFsygongsound = audioplayer（y，fs）;玩（冈索）

假设您复制gongSoundobject handle to another variable (Gongsound2):

Gongsound2= gongSound;

变量gongSound和Gongsound2are copies of the same handle and, therefore, refer to the same audio source. Access theaudioplayerinformation using either variable.

例如，set the sample rate for the gong audio source by assigning a new value to theSampleRate财产。首先获得当前的采样率，然后设置新的样本率：

sr = gongsound.mamplate;disp（SR）

8192

gongsound.samplerate = sr*2;

You can useGongsound2访问相同的音频来源：

disp(gongSound2.SampleRate)

16384

Play the gong sound with the new sample rate:

play(gongSound2)

Handle Objects Modified in Functions

当您将参数传递给函数时，该函数将从工作区中复制变量，其中将函数调用到函数工作区中的参数变量中。

将非手动变量传递到函数不会影响呼叫者工作区中的原始变量。例如，myFuncmodifies a local variable calledvar, but when the function ends, the local variablevarno longer exists:

功能myfunc（var）var = var + 1;end

Define a variable and pass it tomyfunc:

x = 12; myFunc(x)

的价值x执行后没有更改myFunc(x):

disp(x)

12

ThemyFunc函数可以返回修改后的值，您可以将其分配给相同的变量名称（x) or another variable.

功能out = myFunc(var) out = var + 1;end

Modify a value inmyfunc:

x = 12; x = myFunc(x); disp(x)

13

当参数是句柄变量时，该函数仅复制句柄，而不是该句柄识别的对象。两个处理（原始副本和本地副本）都涉及同一对象。

When the function modifies the data referred to by the object handle, those changes are accessible from the handle variable in the calling workspace without the need to return the modified object.

例如，修改缩影函数更改audioplayersample rate:

功能修改缩影(audioObj,sr) audioObj.SampleRate = sr;end

Create anaudioplayer对象并将其传递给修改缩影功能:

loadgongFsygongsound = audioplayer（y，fs）;disp（gongsound.mamplate）

8192

修改缩影(gongSound,16384) disp(gongSound.SampleRate)

16384

The修改缩影功能does not need to return a modifiedgongSoundobject becauseaudioplayer对象是处理对象。

Determine If an Object Is a Handle

Handle objects are members of thehandle班级。因此，您始终可以使用isa功能。isareturns logical真的(1) when testing for a handle variable:

loadgongFsygongsound = audioplayer（y，fs）;isa(gongSound,'handle')

To determine if a variable is a valid handle object, useisa和isvalid:

ifisa(gongSound,'handle') && isvalid(gongSound)。。。end

Deleted Handle Objects

删除手柄对象后，引用对象的句柄变量仍然存在。这些变量变得无效，因为他们所指的对象不再存在。打电话删除on the object removes the object, but does not clear handle variables.

例如，创建一个audioplayer目的：

loadgongFsygongsound = audioplayer（y，fs）;

The output argument,gongSound，是一个句柄变量。打电话删除删除s the object along with the audio source information it contains:

删除(gongSound)

However, the handle variable still exists:

disp(gongSound)

handle to deleted audioplayer

Thewhoscommand showsgongSoundas anaudioplayer目的：

whos

Name Size Bytes Class Attributes Fs 1x1 8 double gongSound 1x1 0 audioplayer y 42028x1 336224 double

The handlegongSound不再指一个有效的对象，如isvalid处理方法：

isvalid(gongSound)

ans = logical 0

打电话删除on a deleted handle does nothing and does not cause an error. You can pass an array containing both valid and invalid handles to删除。MATLAB删除有效的手柄，但在遇到已经无效的手柄时不会发出错误。

You cannot access properties with the invalid handle variable:

gongSound.SampleRate

Invalid or deleted object.

Functions and methods that access object properties cause an error:

玩（冈索）

Invalid or deleted object.

要删除变量，gongSound， 利用清除:

清除gongSoundwhos

名称大小字节类属性FS 1x1 8双Y 42028X1 336224双重