我正在使用Matlab / Simulink中的一个简单的系统对象。
看起来像这样：
classdef realtime_header_detectorSO < matlab.System & matlab.system.mixin.Propagates
% correlateHeader
%
% This template includes the minimum set of functions required
% to define a System object with discrete state.
properties
Header
%nrOfBitsInPreviousStep=0;
s=100;
d=zeros(1,s);
end
properties (DiscreteState)
end
properties (Access = private)
max_nr_of_packets=20;
max_packet_length_in_bytes=300;
current_packet=1;
% Pre-computed constants.
% h = commsrc.pn('GenPoly', [9 5 0],'NumBitsOut', 8,'InitialStates',ones(1,9));
% data=logical(zeros(max_nr_of_packets,max_packet_length_in_bytes*8));
end
methods (Access = protected)
function setupImpl(obj,u)
% Implement tasks that need to be performed only once,
% such as pre-computed constants.
end
function [maxCorr]= stepImpl(obj,u)
eml.extrinsic('num2str');
coder.extrinsic('sprintf');
% Implement algorithm. Calculate y as a function of
% input u and discrete states.
%y = size(u,1);
symbols=sign(u);
c=abs(conv(flipud(obj.Header),[symbols; symbols]));
maxCorr=max(c);
% maxCorr
if(maxCorr==36)
idx36=find(c(1:size(symbols,1))==36);
disp('header(s) detected at the following location(s) in bytes:');
disp(sprintf('%15.4f \n',idx36/8));
nrOfSymbols=size(symbols,1);
disp(['out of nr. of total symbols: ' num2str(nrOfSymbols)]);
disp('------');
% maxCorr
end
% y=obj.pBufferIdx;
end
function resetImpl(obj)
% Initialize discrete-state properties.
end
function varargout = isOutputFixedSizeImpl(~)
varargout = {true};
end
function varargout = getOutputSizeImpl(obj)
varargout = {[1 1]};
end
end
end
然而，当我编译/运行它时，我收到以下错误：
The System object name 'realtime_header_detectorSO' specified in MATLAB System block 'freqScanningRT/Sync and
Find Header/detect header' is invalid.
Caused by:
Undefined function or variable 's'.
但是（！）以下代码编译并运行正常：
classdef realtime_header_detectorSO < matlab.System & matlab.system.mixin.Propagates
% correlateHeader
%
% This template includes the minimum set of functions required
% to define a System object with discrete state.
properties
Header
%nrOfBitsInPreviousStep=0;
s=100;
% d=zeros(1,s);
end
properties (DiscreteState)
end
properties (Access = private)
max_nr_of_packets=20;
max_packet_length_in_bytes=300;
current_packet=1;
% Pre-computed constants.
% h = commsrc.pn('GenPoly', [9 5 0],'NumBitsOut', 8,'InitialStates',ones(1,9));
% data=logical(zeros(max_nr_of_packets,max_packet_length_in_bytes*8));
end
methods (Access = protected)
function setupImpl(obj,u)
% Implement tasks that need to be performed only once,
% such as pre-computed constants.
end
function [maxCorr]= stepImpl(obj,u)
eml.extrinsic('num2str');
coder.extrinsic('sprintf');
% Implement algorithm. Calculate y as a function of
% input u and discrete states.
%y = size(u,1);
disp(obj.s);
symbols=sign(u);
c=abs(conv(flipud(obj.Header),[symbols; symbols]));
maxCorr=max(c);
% maxCorr
if(maxCorr==36)
idx36=find(c(1:size(symbols,1))==36);
disp('header(s) detected at the following location(s) in bytes:');
disp(sprintf('%15.4f \n',idx36/8));
nrOfSymbols=size(symbols,1);
disp(['out of nr. of total symbols: ' num2str(nrOfSymbols)]);
disp('------');
% maxCorr
end
% y=obj.pBufferIdx;
end
function resetImpl(obj)
% Initialize discrete-state properties.
end
function varargout = isOutputFixedSizeImpl(~)
varargout = {true};
end
function varargout = getOutputSizeImpl(obj)
varargout = {[1 1]};
end
end
end
因此，我可以s中的stepImpl(obj,u)访问obj.s s但我无法访问定义它的属性块中的s！
现在这令人困惑。
是否可以在属性块中访问 function setupImpl(obj,u)
% Implement tasks that need to be performed only once,
% such as pre-computed constants.
d=zeros(1,obj.s);
end
？
问题是我必须使用属性块，因为如果我尝试这个：
Error due to multiple causes.
Caused by:
Problem creating simulation target MEX-file for model 'freqScanningRT'.
Simulink detected an error
'Computed maximum size is not bounded.
Static memory allocation requires all sizes to be bounded.
The computed size is [1 x :?].'.
The error occurred for MATLAB System block 'freqScanningRT/Sync and Find Header/detect header'. See line
34, column 15 in file
'path/realtime_header_detectorSO.m'.
The error was detected during code generation phase.
Start code generation report.
To prevent this error, use one of the following:
* Modify the System object to avoid code that does not support code generation.
* Change 'Simulate using' parameter to 'Interpreted Execution'.
然后我得到：
properties知道如何引用var io = require('socket.io').listen(1500); //for the socket
io.set('origins', "http://localhost:130"); //the port of the application
io.sockets.on('connection', function (socket) {
// Let everyone know it's working
socket.emit('startup', { message: 'I Am Working!!' });
});
块中的变量吗？
必须有办法做到这一点。
答案 0 :(得分：1)
你应该可以使用
properties
s = 100;
d = zeros(1,100);
end
正确？如果您已将{100}作为s的默认值，则您还应该能够将其作为d默认值的一部分提供。
我猜你正试图避免这样做，因为你感到不舒服重复“100”。但我也猜测，“100”是你的系统所依赖的某种神奇数字;所以，无论如何，无论是否重复，都应该尝试将其作为常量拉出来。
因此，在这种情况下，您可以使用
改进properties (Constant)
MYCONSTANT = 100;
end
properties
% Reference Constant class properties with the class name
s = realtime_header_detectorSO.MYCONSTANT;
d = zeros(1, realtime_header_detectorSO.MYCONSTANT);
end
您无法完成您最初尝试的操作 - 在定义另一个属性时，无法在属性定义块中引用一个属性的名称（即使您可以很好地引用它在方法内）。我想我明白为什么你会发现这令人困惑 - 但要清除你的困惑，请注意你无法保证 order ，其中MATLAB实例化属性的默认值。如果它在创建d之前尝试创建s，则显然会失败。
答案 1 :(得分：0)
您可以通过初始化构造函数中的属性来一起避免此问题。