我正在编辑用角度6编写的项目的一些代码，将项目升级到角度7后，我遇到了有关使用此“！”的一些问题！组件的html文件中的符号。
<div *ngIf="parentField == null">
<a href (click)="!!setEntity(entity)">{{ entity.name }}</a>
</div>
如您在上方看到的，使用了“！”登录我的模板。我不知道它的含义或对该符号对我的组件的影响。如果我删除了这些符号，则该应用会以开发模式重新加载自身。
在生产模式下编译它时，还会引发此错误。
An expression of type 'void' cannot be tested for truthiness
请参见下面我更新的依赖项
dependencies": {
"@angular/animations": "^7.2.15",
"@angular/cdk": "^7.2.0",
"@angular/common": "^7.2.15",
"@angular/compiler": "^7.2.15",
"@angular/core": "^7.2.15",
"@angular/forms": "^7.2.15",
"@angular/material": "^7.2.0",
"@angular/platform-browser": "^7.2.15",
"@angular/platform-browser-dynamic": "^7.2.15",
"@angular/router": "^7.2.15",
"@fortawesome/fontawesome-free-brands": "^5.0.13",
"@fortawesome/fontawesome-free-regular": "^5.0.13",
"@fortawesome/fontawesome-free-solid": "^5.0.13",
"@handsontable/angular": "^3.0.0",
"core-js": "^2.5.4",
"ngx-bootstrap": "^3.0.0",
"npm": "^5.6.0",
"rxjs": "^6.5.2",
"zone.js": "^0.8.29"
},
"devDependencies": {
"@angular-devkit/build-angular": "^0.11.4",
"@angular/cli": "~7.3.9",
"@angular/compiler-cli": "^7.2.15",
"@angular/language-service": "^7.2.15",
"@types/jasmine": "~2.8.6",
"@types/jasminewd2": "~2.0.3",
"@types/node": "~8.9.4",
"angular-ide": "^0.9.55",
"codelyzer": "~4.2.1",
"jasmine-core": "~2.99.1",
"jasmine-spec-reporter": "~4.2.1",
"karma": "~1.7.1",
"karma-chrome-launcher": "~2.2.0",
"karma-coverage-istanbul-reporter": "~2.0.0",
"karma-jasmine": "~1.1.1",
"karma-jasmine-html-reporter": "^0.2.2",
"protractor": "^5.4.2",
"ts-node": "^7.0.0",
"tslint": "^5.11.0",
"typescript": "~3.2.4"
}
等待您的帮助！