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Overview

The PrestamoService handles all operations related to book loans (préstamos) including requesting loans, listing loans, and managing loan approvals/rejections. It provides different methods for regular users and administrators. Location: src/app/core/services/prestamo.ts

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Constructor

private http = inject(HttpClient);
Uses Angular’s inject() function to obtain HttpClient instance.

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Properties

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apiUrl
string
default:"${environment.apiUrl}/prestamos"
Base URL for prestamo endpoints, configured from environment settings.

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Methods

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solicitar()

Requests a loan for a specific book. Available to authenticated users. 
solicitar(libroId: number): Observable<any>
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libroId
number
required
The unique identifier of the book to borrow
Returns: Observable<any> - Plain text response from server Response Type: Text (uses responseType: 'text') Example: 
const bookId = 42;

this.prestamoService.solicitar(bookId).subscribe({
  next: (response) => {
    console.log('Loan requested:', response);
    alert('Solicitud de préstamo enviada exitosamente');
  },
  error: (error) => {
    if (error.status === 400) {
      alert('El libro no está disponible');
    } else {
      console.error('Error requesting loan:', error);
    }
  }
});
API Endpoint: POST ${apiUrl}/solicitar/{libroId} Request Body: Empty object {} Use Case: When a user wants to borrow a book from the catalog

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getAll()

Retrieves all loan requests from all users. Admin-only endpoint. 
getAll(): Observable<Prestamo[]>
Returns: Observable<Prestamo[]> - Array of all loan requests
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Prestamo[]
array
Array of loan objects
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id
number
Unique loan identifier
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fechaSolicitud
string
Date when the loan was requested (ISO 8601 format)
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fechaDevolucion
string
Date when the book was returned (if applicable)
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estado
string
Loan status: “PENDIENTE”, “APROBADO”, or “RECHAZADO”
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libro
Libro
Complete book object (id, titulo, portada, genero, autores, etc.)
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usuario
any
User information from Spring Boot backend
Example: 
// Admin component
this.prestamoService.getAll().subscribe({
  next: (prestamos) => {
    console.log(`Found ${prestamos.length} loan requests`);
    this.allLoans = prestamos;
    
    // Filter by status
    this.pendingLoans = prestamos.filter(p => p.estado === 'PENDIENTE');
    this.approvedLoans = prestamos.filter(p => p.estado === 'APROBADO');
  },
  error: (error) => {
    console.error('Error fetching loans:', error);
  }
});
API Endpoint: GET ${apiUrl}/todos Authorization: Requires ROLE_ADMIN

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getMisPrestamos()

Retrieves loan requests for the currently authenticated user. 
getMisPrestamos(): Observable<Prestamo[]>
Returns: Observable<Prestamo[]> - Array of current user’s loan requests Example: 
// User component
this.prestamoService.getMisPrestamos().subscribe({
  next: (misPrestamos) => {
    console.log(`You have ${misPrestamos.length} loan requests`);
    this.myLoans = misPrestamos;
    
    // Show status to user
    misPrestamos.forEach(prestamo => {
      console.log(`${prestamo.libro.titulo} - ${prestamo.estado}`);
    });
  },
  error: (error) => {
    console.error('Error fetching my loans:', error);
  }
});
API Endpoint: GET ${apiUrl}/mios Authorization: Requires authentication (ROLE_USER or ROLE_ADMIN) Use Case: Displaying user’s loan history and current requests

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aprobar()

Approves a pending loan request. Admin-only operation. 
aprobar(id: number): Observable<any>
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id
number
required
The unique identifier of the loan to approve
Returns: Observable<any> - Plain text response from server Response Type: Text (uses responseType: 'text') Example: 
const prestamoId = 15;

this.prestamoService.aprobar(prestamoId).subscribe({
  next: (response) => {
    console.log('Loan approved:', response);
    alert('Préstamo aprobado exitosamente');
    this.loadPendingLoans(); // Refresh the list
  },
  error: (error) => {
    console.error('Error approving loan:', error);
  }
});
API Endpoint: POST ${apiUrl}/aprobar/{id} Request Body: Empty object {} Authorization: Requires ROLE_ADMIN Behavior: Changes loan status from PENDIENTE to APROBADO

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rechazar()

Rejects a pending loan request. Admin-only operation. 
rechazar(id: number): Observable<any>
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id
number
required
The unique identifier of the loan to reject
Returns: Observable<any> - Plain text response from server Response Type: Text (uses responseType: 'text') Example: 
const prestamoId = 15;

if (confirm('¿Está seguro de rechazar este préstamo?')) {
  this.prestamoService.rechazar(prestamoId).subscribe({
    next: (response) => {
      console.log('Loan rejected:', response);
      alert('Préstamo rechazado');
      this.loadPendingLoans(); // Refresh the list
    },
    error: (error) => {
      console.error('Error rejecting loan:', error);
    }
  });
}
API Endpoint: POST ${apiUrl}/rechazar/{id} Request Body: Empty object {} Authorization: Requires ROLE_ADMIN Behavior: Changes loan status from PENDIENTE to RECHAZADO

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Complete Usage Examples

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User Component (Request and View Loans)

import { Component, OnInit, inject } from '@angular/core';
import { PrestamoService } from '../core/services/prestamo';
import { Prestamo } from '../core/models/prestamo';

@Component({
  selector: 'app-my-loans',
  templateUrl: './my-loans.html'
})
export class MyLoansComponent implements OnInit {
  prestamoService = inject(PrestamoService);
  myLoans: Prestamo[] = [];
  loading = false;

  ngOnInit() {
    this.loadMyLoans();
  }

  loadMyLoans() {
    this.loading = true;
    this.prestamoService.getMisPrestamos().subscribe({
      next: (prestamos) => {
        this.myLoans = prestamos;
        this.loading = false;
      },
      error: (err) => {
        console.error('Error loading loans:', err);
        this.loading = false;
      }
    });
  }

  requestLoan(libroId: number) {
    this.prestamoService.solicitar(libroId).subscribe({
      next: (response) => {
        alert('Préstamo solicitado exitosamente');
        this.loadMyLoans(); // Refresh to show new request
      },
      error: (err) => {
        alert('Error al solicitar préstamo');
      }
    });
  }

  getStatusClass(estado: string): string {
    switch(estado) {
      case 'PENDIENTE': return 'badge-warning';
      case 'APROBADO': return 'badge-success';
      case 'RECHAZADO': return 'badge-danger';
      default: return 'badge-secondary';
    }
  }
}

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Admin Component (Manage All Loans)

import { Component, OnInit, inject } from '@angular/core';
import { PrestamoService } from '../core/services/prestamo';
import { Prestamo } from '../core/models/prestamo';

@Component({
  selector: 'app-prestamo-list',
  templateUrl: './prestamo-list.html'
})
export class PrestamoListComponent implements OnInit {
  prestamoService = inject(PrestamoService);
  prestamos: Prestamo[] = [];
  filteredPrestamos: Prestamo[] = [];
  selectedFilter: string = 'TODOS';

  ngOnInit() {
    this.loadPrestamos();
  }

  loadPrestamos() {
    this.prestamoService.getAll().subscribe({
      next: (data) => {
        this.prestamos = data;
        this.applyFilter();
      },
      error: (err) => {
        console.error('Error loading loans:', err);
      }
    });
  }

  applyFilter() {
    if (this.selectedFilter === 'TODOS') {
      this.filteredPrestamos = this.prestamos;
    } else {
      this.filteredPrestamos = this.prestamos.filter(
        p => p.estado === this.selectedFilter
      );
    }
  }

  aprobarPrestamo(id: number) {
    this.prestamoService.aprobar(id).subscribe({
      next: () => {
        alert('Préstamo aprobado');
        this.loadPrestamos();
      },
      error: (err) => {
        console.error('Error approving loan:', err);
      }
    });
  }

  rechazarPrestamo(id: number) {
    if (confirm('¿Rechazar este préstamo?')) {
      this.prestamoService.rechazar(id).subscribe({
        next: () => {
          alert('Préstamo rechazado');
          this.loadPrestamos();
        },
        error: (err) => {
          console.error('Error rejecting loan:', err);
        }
      });
    }
  }
}

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Data Model

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Prestamo Interface

import { Libro } from './libro';

export interface Prestamo {
  id: number;
  fechaSolicitud: string;
  fechaDevolucion?: string;
  estado: 'PENDIENTE' | 'APROBADO' | 'RECHAZADO';
  libro: Libro;
  usuario: any; // Complete user object from Spring Boot
}

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Estado (Status) Values

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PENDIENTE
string
Loan request is awaiting admin approval
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APROBADO
string
Loan has been approved by an administrator
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RECHAZADO
string
Loan has been rejected by an administrator

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Error Handling

Common error scenarios: 
this.prestamoService.solicitar(libroId).subscribe({
  next: (response) => { /* success */ },
  error: (error) => {
    if (error.status === 400) {
      console.error('Book not available or already requested');
    } else if (error.status === 401) {
      console.error('Authentication required');
    } else if (error.status === 403) {
      console.error('Access forbidden');
    } else if (error.status === 404) {
      console.error('Book not found');
    } else {
      console.error('Unexpected error:', error);
    }
  }
});

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Authorization Requirements

MethodRequired RoleDescription
solicitar()ROLE_USER or ROLE_ADMINAny authenticated user
getMisPrestamos()ROLE_USER or ROLE_ADMINAny authenticated user
getAll()ROLE_ADMINAdmin only
aprobar()ROLE_ADMINAdmin only
rechazar()ROLE_ADMINAdmin only

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See Also

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