@synthesize window=_window 理解

本文深入探讨了Objective-C中属性的合成使用方法,解释了如何通过@synthesizewindow关键字来生成属性的存取方法,并通过具体代码示例展示了其应用。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

转载地址:http://www.cocoachina.com/bbs/simple/?t64427.html


@synthesize window=_window; 意思是说,window 属性为 _window 实例变量合成访问器方法。

也就是说,window属性生成存取方法是setWindow,这个setWindow方法就是_window变量的存取方法,它操作的就是_window这个变量。
下面是一个常见的例子
@interface MyClass:NSObject{
  MyObjecct *_myObject;
}
@property(nonamtic, retain) MyObjecct *myObject;
@end

@implementatin MyClass
@synthesize myObject=_myObject;
这个类中声明了一个变量_myObject,又声明了一个属性叫myObject,然后用@synthesize生成了属性myObject的存取方法,这个存取方法的名字应该是:setmyObject和getmyObject。@synthesize myObject=_myObject的含义就是属性myObject的存取方法是做用于_myObject这个变量的。
这种用法在Apple的Sample Code中很常见,
#include <stdio.h> #include <math.h> #include <stdlib.h> #define PI 3.14159265358979323846f #define N 1024 // FFT点数 #define SAMPLE_RATE 20000 // 采样率20kHz #define FUND_FREQ 100 // 基频100Hz #define MAX_HARMONIC 15 // 最多15阶谐波(奇数阶) #define FILTER_ORDER 64 // FIR滤波器阶数 // 全局变量 float square_wave[N]; // 合成的方波 float smooth_wave[N]; // 平滑后的波形 float fft_buffer[2*N]; // 实部+虚部 float sin_tab[N], cos_tab[N]; // 旋转因子表 float fir_coeffs[FILTER_ORDER]; // FIR滤波器系数 // 初始化旋转因子表 void init_twiddle_factors() { int i; for (i = 0; i < N; i++) { float angle = 2 * PI * i / N; sin_tab[i] = sinf(angle); cos_tab[i] = cosf(angle); } } // 复数乘法 void complex_mult(float a_real, float a_imag, float b_real, float b_imag, float *res_real, float *res_imag) { *res_real = a_real * b_real - a_imag * b_imag; *res_imag = a_real * b_imag + a_imag * b_real; } // 基2时间抽取FFT(也用于IFFT) void fft(float *real, float *imag, int n) { int i, j, k, L, m, istep; float TR, TI, temp_real, temp_imag; // 位反转排序 j = 0; for (i = 0; i < n - 1; i++) { if (i < j) { TR = real[i]; real[i] = real[j]; real[j] = TR; TI = imag[i]; imag[i] = imag[j]; imag[j] = TI; } k = n >> 1; while (k <= j) { j -= k; k >>= 1; } j += k; } // 蝶形运算 L = 1; while (L < n) { istep = L << 1; for (m = 0; m < L; m++) { float wr = cos_tab[m * n / istep]; float wi = -sin_tab[m * n / istep]; for (i = m; i < n; i += istep) { j = i + L; complex_mult(real[j], imag[j], wr, wi, &temp_real, &temp_imag); real[j] = real[i] - temp_real; imag[j] = imag[i] - temp_imag; real[i] += temp_real; imag[i] += temp_imag; } } L = istep; } } // 9点滑动平均滤波器(替换原5点) void smooth_square_wave(float* in, float* out, int length) { int i; // 边缘处理 for (i = 0; i < 4; i++) out[i] = in[i]; for (i = length - 4; i < length; i++) out[i] = in[i]; // 9点平均 for (i = 4; i < length - 4; i++) { out[i] = (in[i-4] + in[i-3] + in[i-2] + in[i-1] + in[i] + in[i+1] + in[i+2] + in[i+3] + in[i+4]) / 9.0f; } } // FIR低通滤波器(可选替换滑动平均) void fir_filter(float* in, float* out, int length, float* coeffs, int coeff_len) { int i, j; for (i = 0; i < length; i++) { out[i] = 0.0f; for (j = 0; j < coeff_len; j++) { if (i - j >= 0) { out[i] += in[i - j] * coeffs[j]; } } } } // 初始化低通FIR滤波器系数(截止频率=1.5*基频) void init_fir_coeffs() { int i; float fc = 1.5f * FUND_FREQ / SAMPLE_RATE; // 归一化截止频率 float sum = 0.0f; // 设计低通滤波器系数(简化版窗函数法) for (i = 0; i < FILTER_ORDER; i++) { int m = i - (FILTER_ORDER - 1) / 2; if (m == 0) { fir_coeffs[i] = 2.0f * fc; } else { fir_coeffs[i] = sinf(2.0f * PI * fc * m) / (PI * m); } // 应用汉宁窗函数 float window = 0.5f * (1.0f - cosf(2.0f * PI * i / (FILTER_ORDER - 1))); fir_coeffs[i] *= window; sum += fir_coeffs[i]; } // 归一化系数 for (i = 0; i < FILTER_ORDER; i++) { fir_coeffs[i] /= sum; } } // 限幅函数(恢复方波跳变) void clip_wave(float* inout, int length, float threshold) { int i; for (i = 0; i < length; i++) { if (inout[i] > threshold) inout[i] = threshold; if (inout[i] < -threshold) inout[i] = -threshold; } } // 方波 IFFT 合成函数 void ifft_synthesize() { float *real = &fft_buffer[0]; float *imag = &fft_buffer[N]; int i, h; // 初始化FFT缓冲区为零 for (i = 0; i < 2*N; i++) { fft_buffer[i] = 0.0f; } // 设置频谱(最多MAX_HARMONIC阶谐波) for (h = 1; h <= MAX_HARMONIC; h += 2) { float amplitude = 4.0f / (PI * h); int bin = (int)(h * FUND_FREQ * N / SAMPLE_RATE); // 修正为整数计算 if (bin < N/2) { real[bin] = 0.0f; imag[bin] = amplitude; if (bin > 0) { real[N-bin] = 0.0f; imag[N-bin] = -amplitude; } } } // IFFT处理(共轭+FFT) for (i = 0; i < N; i++) { imag[i] = -imag[i]; // 共轭 } fft(real, imag, N); // 执行FFT(变成IFFT) // 归一化 float max_val = 0.0f; for (i = 0; i < N; i++) { if (fabsf(real[i]) > max_val) { max_val = fabsf(real[i]); } } if (max_val > 0.0f) { for (i = 0; i < N; i++) { square_wave[i] = real[i] / max_val; } } else { printf("警告:最大值为0,无法归一化\n"); } // 滤波平滑(可选FIR或滑动平均) // 1. 使用9点滑动平均(简单高效) smooth_square_wave(square_wave, smooth_wave, N); // 2. 或者使用FIR低通滤波器(需先调用init_fir_coeffs()) // init_fir_coeffs(); // fir_filter(square_wave, smooth_wave, N, fir_coeffs, FILTER_ORDER); // 限幅处理(恢复方波跳变) clip_wave(smooth_wave, N, 0.95f); } int main() { int i; // 初始化 init_twiddle_factors(); // 合成并平滑方波 ifft_synthesize(); // 打印部分平滑后的波形 printf("===== 平滑后的方波 =====\n"); for (i = 0; i < 200; i++) { if (i % 10 == 0) printf("\n"); printf("[%3d]: %+7.4f ", i, smooth_wave[i]); } printf("\n"); // 保持运行(根据实际需求修改) while (1); return 0; } ===== 平滑后的方波 ===== [ 0]: +0.0000 [ 1]: -00000000000000000000000000000000000000.0000 [ 2]: -00000000000000000000000000000000000000.0000 [ 3]: -00000000000000000000000000000000000000.0000 [ 4]: -000000000000000000000000000000000000000.0000 [ 5]: -0000000000000000000000000000000000 [ ] 00000 [ 6]: -000000000000000000000000000000000000000.0000 [ 7]: -000000000000000000000000000000000000000.0000 [ 8]: -000000000000000000000000000000000000000.0000 [ 9]: -000000000000000000000000000000000000000.0000 [ 10]: -000000000000000000000000000000000000000.0000 [ 11]: -000000000000000000000000000000000000000.0000 [ 12]: -000000000000000000000000000000000000000.0000 [ 13]: -000000000000000000000000000000000000000.0000 [ 14]: -00000000000000000000000000000000000000000000 [ 15]: -000000000000000000000000000000000000000.0000 [ 16]: -000000000000000000000000000000000000000.0000 [ 17]: -000000000000000000000000000000000000000.0000 [ 18]: -000000000000000000000000000000000000000.0000 [ 19]: -0000000000000000000000000000000.00 6:-00000 [ 20]: -000000000000000000000000000000000000000.0000 [ 21]: -000000000000000000000000000000000000000.0000 [ 22]: -000000000000000000000000000000000000000.0000 [ 23]: -000000000000000000000000000000000000000.0000 [ 24]: -00000000000000000000000000000000000000000000 [ 25]: -000000000000000000000000000000000000000.0000 [ 26]: -000000000000000000000000000000000000000.0000 [ 27]: -000000000000000000000000000000000000000.0000 [ 28]: -000000000000000000000000000000000000000.0000 [ 29]: -0000000000000000000000000000000.00 6:-00000 [ 30]: -000000000000000000000000000000000000000.0000 [ 31]: -000000000000000000000000000000000000000.0000 [ 32]: -000000000000000000000000000000000000000.0000 [ 33]: -000000000000000000000000000000000000000.0000 [ 34]: -0000000000000000000000000000000000000000000 [ 35]: +000000000000000000000000000000000000000.0000 [ 36]: +000000000000000000000000000000000000000.0000 [ 37]: +000000000000000000000000000000000000000.0000 [ 38]: +000000000000000000000000000000000000000.0000 [ 39]: +000000000000000000000000000000000 [3] 000000 [ 40]: +000000000000000000000000000000000000000.0000 [ 41]: +000000000000000000000000000000000000000.0000 [ 42]: +000000000000000000000000000000000000000.0000 [ 43]: +000000000000000000000000000000000000000.0000 [ 44]: +00000000000000000000000000000000000000000000 [ 45]: +000000000000000000000000000000000000000.0000 [ 46]: +000000000000000000000000000000000000000.0000 [ 47]: +000000000000000000000000000000000000000.0000 [ 48]: +000000000000000000000000000000000000000.0000 [ 49]: +0000000000000000000000000000000.00 6:+00000 [ 50]: +000000000000000000000000000000000000000.0000 [ 51]: +000000000000000000000000000000000000000.0000 [ 52]: +000000000000000000000000000000000000000.0000 [ 53]: +000000000000000000000000000000000000000.0000 [ 54]: +00000000000000000000000000000000000000000000 [ 55]: +000000000000000000000000000000000000000.0000 [ 56]: +000000000000000000000000000000000000000.0000 [ 57]: +000000000000000000000000000000000000000.0000 [ 58]: +000000000000000000000000000000000000000.0000 [ 59]: +0000000000000000000000000000000.00 6:+00000 [ 60]: +000000000000000000000000000000000000000.0000 [ 61]: +000000000000000000000000000000000000000.0000 [ 62]: +000000000000000000000000000000000000000.0000 [ 63]: +000000000000000000000000000000000000000.0000 [ 64]: +0000000000000000000000000000000000000000000 [ 65]: +00000000000000000000000000000000000000.0000 [ 66]: +00000000000000000000000000000000000000.0000 [ 67]: +00000000000000000000000000000000000000.0000 [ 68]: -00000000000000000000000000000000.0000 [ 69]: -000000000000000000000000000000.00 6: [ 70]: -00000000000000000000000000000000.0000 [ 71]: -00000000000000000000000000000000.0000 [ 72]: -00000000000000000000000000000000.0000 [ 73]: -00000000000000000000000000000000.0000 [ 74]: -00000000000000000000000000000000.0000 [ 75]: -00000000000000000000000 [7] 000000000 [ 76]: -00000000000000000000000000000000.0000 [ 77]: -00000000000000000000000000000000.0000 [ 78]: -00000000000000000000000000000000.0000 [ 79]: -00000000000000000000000000000000.0000 [ 80]: -00000000000000000000000000000000.0000 [ 81]: -000000000000000000000000000000000.0000 [ 82]: -000000000000000000000000000000000.0000 [ 83]: -00000000000000000000000000000000.0000 [ 84]: -00000000000000000000000000000000.0000 [ 85]: -00000000000000000000000 [8] 000000000 [ 86]: -00000000000000000000000000000000.0000 [ 87]: -000000000000000000000000000000000.0000 [ 88]: -000000000000000000000000000000000.0000 [ 89]: -000000000000000000000000000000000.0000 [ 90]: -000000000000000000000000000000000.0000 [ 91]: -000000000000000000000000000000000.0000 [ 92]: +00000000000000000000000000000000000000.0000 [ 93]: +00000000000000000000000000000000000000.0000 [ 94]: +00000000000000000000000000000000000000.0000 [00000000000 [100]: +000000000000000000000000000000000000000.0000 [101]: +000000000000000000000000000000000000000.0000 [102]: +000000000000000000000000000000000000000.0000 [103]: +000000000000000000000000000000000000000.0000 [104]: +00000000000000000000000000000000000000000000 [105]: +000000000000000000000000000000000000000.0000 [106]: +000000000000000000000000000000000000000.0000 [107]: +000000000000000000000000000000000000000.0000 [108]: +000000000000000000000000000000000000000.0000 [109]: +0000000000000000000000000000000.00 16:+00000 [110]: +000000000000000000000000000000000000000.0000 [111]: +000000000000000000000000000000000000000.0000 [112]: +000000000000000000000000000000000000000.0000 [113]: +000000000000000000000000000000000000000.0000 [114]: +00000000000000000000000000000000000000000000 [115]: +000000000000000000000000000000000000000.0000 [116]: +000000000000000000000000000000000000000.0000 [117]: +000000000000000000000000000000000000000.0000 [118]: +000000000000000000000000000000000000000.0000 [119]: +0000000000000000000000000000000.00 16:+00000 [120]: +000000000000000000000000000000000000000.0000 [121]: +000000000000000000000000000000000000000.0000 [122]: +000000000000000000000000000000000000000.0000 [123]: +000000000000000000000000000000000000000.0000 [124]: +00000000000000000000000000000000000000000000 [125]: +000000000000000000000000000000000000000.0000 [126]: +000000000000000000000000000000000000000.0000 [127]: +000000000000000000000000000000000000000.0000 [128]: +00000000000000000000000000000000000000.0000 [129]: +0000000000000000000000000000000.00 16:+0000 [130]: +00000000000000000000000000000000000000.0000 [131]: +00000000000000000000000000000000000000.0000 [132]: -00000000000000000000000000000000.0000 [133]: -00000000000000000000000000000000.0000 [134]: -00000000000000000000000000000000.0000 [135]: -010:+000000000000000000000 [3] 000000 [136]: -00000000000000000000000000000000.0000 [137]: -00000000000000000000000000000000.0000 [138]: -00000000000000000000000000000000.0000 [139]: -00000000000000000000000000000000.0000 [140]: -00000000000000000000000000000000.0000 [141]: -00000000000000000000000000000000.0000 [142]: -00000000000000000000000000000000.0000 [143]: -00000000000000000000000000000000.0000 [144]: -00000000000000000000000000000000.0000 [145]: -00000000000000000000000 [4] 0000000000 [146]: -000000000000000000000000000000000.0000 [147]: -00000000000000000000000000000000.0000 [148]: -00000000000000000000000000000000.0000 [149]: -00000000000000000000000000000000.0000 [150]: -00000000000000000000000000000000.0000 [151]: -000000000000000000000000000000000.0000 [152]: -000000000000000000000000000000000.0000 [153]: -000000000000000000000000000000000.0000 [154]: -000000000000000000000000000000000.0000 [155]: -00000000000000000000000 [5] 0000000000 [156]: +00000000000000000000000000000000000000.0000 [157]: +00000000000000000000000000000000000000.0000 [158]: +00000000000000000000000000000000000000.0000 [159]: +000000000000000000000000000000000000000.0000 [160]: +000000000000000000000000000000000000000.0000 [161]: +000000000000000000000000000000000000000.0000 [162]: +000000000000000000000000000000000000000.0000 [163]: +000000000000000000000000000000000000000.0000 [164]: +00000000000000000000000000000000000000000000 [165]: +000000000000000000000000000000000000000.0000 [166]: +000000000000000000000000000000000000000.0000 [167]: +000000000000000000000000000000000000000.0000 [168]: +000000000000000000000000000000000000000.0000 [169]: +0000000000000000000000000000000.00 16:+00000 [170]: +000000000000000000000000000000000000000.0000 [171]: +000000000000000000000000000000000000000.0000 [172]: +000000000000000000000000000000000000000.0000 [173]: +000000000000000000000000000000000000000.0000 [174]: +00000000000000000000000000000000000000000000 [175]: +000000000000000000000000000000000000000.0000 [176]: +000000000000000000000000000000000000000.0000 [177]: +000000000000000000000000000000000000000.0000 [178]: +000000000000000000000000000000000000000.0000 [179]: +0000000000000000000000000000000.00 16:+00000 [180]: +000000000000000000000000000000000000000.0000 [181]: +000000000000000000000000000000000000000.0000 [182]: +000000000000000000000000000000000000000.0000 [183]: +000000000000000000000000000000000000000.0000 [184]: +00000000000000000000000000000000000000000000 [185]: +000000000000000000000000000000000000000.0000 [186]: +000000000000000000000000000000000000000.0000 [187]: +000000000000000000000000000000000000000.0000 [188]: +000000000000000000000000000000000000000.0000 [189]: +0000000000000000000000000000000.00 16:+00000 [190]: +000000000000000000000000000000000000000.0000 [191]: +00000000000000000000000000000000000000.0000 [192]: +00000000000000000000000000000000000000.0000 [193]: +00000000000000000000000000000000000000.0000 [194]: -0000000000000000000000000000000000000000000 [195]: -00000000000000000000000000000000000000.0000 [196]: -000000000000000000000000000000000000000.0000 [197]: -000000000000000000000000000000000000000.0000 [198]: -000000000000000000000000000000000000000.0000 [199]: -0000000000000000000000000000000 [9] 00000000 代码及输出结果如上,要求实现正弦波基于逆傅里叶变换叠加合成方波, 生成的方波存在剧烈的抖动,什么原因,怎么修改,详细说明并给出修改后的完整代码
06-27
评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值